when the shit hits the fan Definition

shit
shite (coarse slang)
noun

1. Excrement or faeces.
2. An act of defecating.
3. derog
Rubbish; nonsense.
4. derog
A despicable person.
5. drug-taking slang
Marijuana or heroin.

verb

intr
shit, shitted, shat, shitting, shited, shiting
1. To defecate.

exclamation

1. Expressing annoyance, disappointment or disgust.

Idiom: beat the shit out of someone (kick the shit out of someone)

To hit or attack them severely.

Idiom: get one's shit together

To get oneself and one's matters organized.

Idiom: No shit

(S)
slang, often ironic
No fooling; You amaze me.

Idiom: scared shitless

To be extremely scared or upset.
Example: I was scared shitless of him

Idiom: shit a brick (shit bricks)

To be very anxious or scared.

Idiom: shit oneself

slang
To be extremely frightened or scared.

Idiom: when the shit hits the fan

slang
When the real trouble or conflict begins.

Idiom: up shit creek

In an extremely difficult or troublesome situation.

Etymology: Anglo-Saxon scitan to defecate.