Meaning:
a. a. michelson 
n.
United States physicist (born in Germany) who collaborated with Morley in the Michelson-Morley experiment (1852-1931)
he Idiom, Proverb
a babe in the woods
"a defenseless person; a naive, young person" He's just a babe in the woods. He needs someone to protect him.
a bee in her bonnet
upset, a bit angry, on edge Aunt Betsy was kind of cranky, like she had a bee in her bonnet.
a big wheel
a person with power, a big shot Bing has been acting like a big wheel since he got promoted.
a bird in the hand is worth two in the bush
having one is better than seeing many When searching for a better job, remember A bird in the hand... .
a bun in the oven
pregnant, expecting a baby Mabel has a bun in the oven. The baby's due in April.
a cheap drunk
a person who gets drunk on one or two drinks Jo admits she's a cheap drunk. Her limit is two drinks.
a checkup
a doctor's examination, a medical examination If you aren't feeling well, go to the doctor for a checkup.
a chip off the old block
a boy who is like his dad, the apple doesn't... Eric is a chip off the old block. He's just like his dad.
a clean bill of health
a good report from the doctor, a good checkup You'll never get a clean bill of health if you eat fat meat!
a dead heat
a race that finishes in a tie for first, dead even A photograph of the finish line proved that it was a dead heat.
a drop in the bucket
a small part, a tiny piece, the tip of the iceberg This donation is only a drop in the bucket, but it is appreciated.
a feather in your cap
an honor, a credit to you, chalk one up for you Because you are Karen's teacher, her award is a feather in your cap.
a fifth wheel
a useless object, an unnecessary device The team already had two guards, so I felt like a fifth wheel.
a fine-toothed comb
a careful search, a search for a detail She read the file carefully - went over it with a fine-toothed comb.
a flash in the pan
a person who does superior work at first I'm looking for a steady worker, not a flash in the pan.
a fly on the wall
able to hear and see what a fly would see and hear I'd like to be a fly on the wall in the Judge's chambers.
a good head
"friendly, generous person; a good egg" Sean is a good head. He'll help at the food bank.
a grandfather clause
a written statement that protects a senior worker They can't demote him because he has a grandfather clause.
a head start
a chance to start ahead of the other runners etc. Give the smallest runner a head start. He can't run very fast.
a heavy day
a busy day, a hard day At the end of a heavy day he likes to sit on the patio and read.
a helping hand
help with a job or task, lend a hand May was always ready with a helping hand.
a hothead
"a person who gets angry easily; hot tempered" Phil, don't be such a hothead. Try to control your anger.
a little hair off the dog
(See hair off the dog)
a lot on the ball
intelligent, smart Melvin may not look intelligent, but he's got a lot on the ball.
a man of the cloth
a minister, a priest, a clergyman Being a man of the cloth, he has studied the Bible.
a pain in the ass
a bother, a lot of trouble Fixing that car every day is a pain in the ass.
a pain in the butt
a person who causes problems, a pain in the ass Hal keeps interrupting me. He's a pain in the butt!
a penny pincher
a person who spends carefully, a thrifty person He used to be a penny pincher, but now he spends freely.
a piece of the action
a share of the profit or prize or loot Those who paid for the winning ticket get a piece of the action.
a roll in the hay
making love, having sex """Want a roll in the hay?"" ""Sure. Do you have a condom?"""
a shot in the arm
energy, encouragement, a lift Billy Graham's sermon was inspiring - a shot in the arm.
a shot in the dark
a wild guess, a try, hazard a guess His answer was incorrect. It was a shot in the dark.
a slip of the tongue
a spoken error or mistake, a word that slips out I said brew instead of blue. It was a slip of the tongue.
a snowball's chance in hell
little or no chance to succeed If I write the test now, I won't have a snowball's chance in hell.
a stitch of clothes
(See didn't have a stitch of clothes on)
a wolf in sheep's clothing
an evil person who looks innocent The priest looked harmless, but he was a wolf in sheep's clothing.
a word to the wise is sufficient
a wise person understands when he hears a key word I can't discuss the plan, but a word to the wise is sufficient: progress.
above and beyond the call of duty
much more than expected, go the extra mile Her extra work was above and beyond the call of duty.
above the law
not required to obey laws, privileged Just because he's rich, he thinks he's above the law.
absence makes the heart grow fonder
when friends are apart they like each other more When she's away I'm very lonely. Absence does make the heart grow fonder.
ace in the hole
a hidden strength or talent Sam's ace in the hole is honesty, which his clients soon discover.
Achilles' heel
a weakness, a vulnerable place Jewelry is my Achilles' heel. I buy too much jewelry.
across the board
affecting all people, applies to everything We want a salary increase across the board - for all positions.
add fuel to the fire
cause more anger, aggravate a problem He's angry. Telling him bad news will add fuel to the fire.
against the grain
against the natural way, rub the wrong way Some words go against the grain. Their spellings aren't natural.
ahead of the game
finished your work, paid all the bills, caught up With all these expenses, we can't seem to get ahead of the game.
ahead of time
early We started the meeting ahead of time so we could go home early.
airhead
(See an airhead)
all hell broke loose
people did crazy things, everybody was fighting When the fire alarm sounded, all hell broke loose.
all over but the shouting
(See it's all over but the shouting)