A colloquial suffix attached to a verb stem (often the -masu stem) that adds the sense of continuing to do something or doing it intensely; conveys emphatic or vigorous action.
彼は冗談に笑いこけて、しばらく止まらなかった。
He laughed heartily at the joke and couldn't stop for a while.
疲れて公園のベンチで寝こけてしまった。
Exhausted, I fell sound asleep on a bench in the park.
感動して彼女は泣きこけた。
She cried uncontrollably with emotion.