godan verb (-ku), transitive verb
expel from the body; let out (a fart)
Colloquial and somewhat crude; used for bodily emissions, especially farting. Often in the phrase 屁をこく.
That guy farted again.
godan verb (-ku), transitive verb
utter (lies, nonsense); spout (bullshit)
Vulgar; used for saying something worthless or false. Common with 嘘, ほざく, or でたらめ. Often in the pattern 〜をこく.
嘘をこくな！
Don't talk bullshit!
あいつはいつもでたらめをこいている。
He's always spouting nonsense.
godan verb (-ku), transitive verb
Highly colloquial and vulgar; a crude substitute for する in certain fixed expressions, such as びっくらこいた (was surprised). Not freely productive.
See also: びっくらこいた
びっくらこいたよ、急に現れるから。
You scared the shit out of me, appearing so suddenly.