Idioms compilation (different topics)

Ants in one's pants

Unable to sit still or remain calm out of nervousness or excitement.

The birds and the bees

Sex education.

Cat nap

A short sleep.

Cat's got one's tongue

Said about someone who doesn't speak (usually due to shyness).

Chicken out

To decide not to do something out of fear (usually just before).

Clam up = shut up like a clam

Become quiet suddenly.

Copy cat

A person who does the same thing as someone else.

Dog days

Very hot days.

Dropping like flies

Dying/giving up quickly.

Eager beaver

A person who is excited about doing certain work.

Fishy

Odd, suspicious.

Have a cow

Get extremely upset (often over something minor).

Hold your horses

Wait and be patient.

Holy cow!

Wow, I'm surprised!

Horse around

Play roughly.

Get the lion's share

Get the greatest percentage.

In the dog house

In trouble with another person.

Kill two birds with one stone

Get two things done at once.

Kitty corner

Diagonal direction.

Let the cat out of the bag

Reveal a secret.

A little bird told me

I heard something (usually secretive or unknown) from someone (not named).

Make a beeline

Go straight for something.

Monkey see, monkey do

Silly/unintelligent people tend to copy each other's actions.

Nest egg

Money saved for the future.

Pig out

Eat a lot of something.

Raining cats and dogs

Raining heavily.

Rat race

Fierce, competitive struggle for power, position, etc.

Smell a rat

Begin to suspect trickery, etc.

Straight from the horse's mouth

Directly from the original source.

Take the bull by the horns

Face a challenge or danger boldly.

Until the cows come home

For a very long time.

All ears

Fully listening.

Break a leg

Good luck.

Cold feet

Nervous just before a big event.

Cost an arm and a leg

Be very expensive.

Cry your heart out

Cry very hard.

Face the music

Meet, stand up to unpleasant consequences.

Flesh and blood

Relative.

Get something off one's chest

Tell someone your problems.

Give a hand, lend a hand

Help (someone) do something.

Have one's head in the clouds

Be unaware or unrealistic about something.

Head over heels

Deeply in love.

Head start

An earlier start.

In over one's head

Taking on a task that you can't handle.

Keep an eye on

Take care of, watch in order to protect.

Keep one's chin up

Try to be cheerful.

Learn by heart

Memorize.

Let one's hair down

Relax, have fun.

Lips are sealed

Promise to keep a secret.

Makes my blood boil

Makes me very angry.

Neck of the woods

Nearby location or region.

An old hand

An experienced person.

Over my dead body

Not unless I'm dead and can't stop you.

Pat on the back

Recognition or a thank-you.

Play something by ear

Do something without a plan.

Pull one's leg

Joke or tease someone.

Rule of thumb

Basic rule (not always followed).

See eye to eye

Agree.

By the skin of one's teeth

Just barely.

Stick your neck out

Help someone a lot, with possible bad consequences for oneself.

Sweet tooth

A love of sugar or sweet things.

Thick in the head

Not very intelligent.

Wash one's hands of something

Stop dealing with an issue or problem.

At the drop of a hat

Without needing any advance notice.

Have a bee in one's bonnet

Something that is annoying someone.

Below the belt

Beyond what is fair or socially acceptable.

Bursting at the seams

Not fitting anymore.

Caught with one's pants down

Unprepared.

Have a card up one's sleeve

Have a secret or reserve plan.

Buckle down

Work extra hard.

Burn a hole in one's pocket

Money that one is tempted to spend.

Dress to kill

Dress in nice or sexy clothes.

Fit like a glove

Fit perfectly (tight to one's body).

Fine-tooth comb

In great detail, extremely carefully.

Fly by the seat of one's pants

Do by instinct, not by plan