살이 쪘어요 (I've gained weight) · 살이 빠졌어요 (I've lost weight)
to gain weight, to put on weight
Example
방학 동안 많이 먹어서 살이 쪘어요.
I ate a lot over vacation and gained weight.
Word parts
Literally 'flesh fills out.'
Good to know
Some Koreans casually say 살 쪘네! to friends, but as a learner it's safer not to comment on weight.