Meaning of Idiom ‘Know Something When You (or one) See It’
To know something when you see it means to be able to recognize or identify something immediately; to be very familiar with something so that you can recognize at once.
Sentence Examples
“I know a con man when I see one. Don’t give this guy any money.”
“I know a good deal when I see one. You should definitely buy that car.”
“Why don’t you trust Nick?” “Because I know a liar when I see one.”
“I know a wolf when I see one and I’m telling you, that was a wolf!”
“I’ve been a lab rat. I know one when I see one.” — X-Men: First Class (2011)
“Teacher or not, I know a spell when I see one. I’ve read all about them.” — Harry Potter and the Sorcerer’s Stone (2001)
“My father trained horses. I’ve raised yearlings since I was five years old. I know a thoroughbred when I see one.” — Ender’s Game (2013)
“…because he thinks I’m gonna make a movie about his life, everything becomes exaggerated and overblown. Trust me, I know a narcissist when I see one.” — A Perfect Getaway (2009)
“I know a gun when I see one, and that’s a gun!” — Wonder Boys (2000)
Origin
Used since at least the early 1800s.
