A term used when you're at the club and the party music is flaccid as heck.

So you bust out the words "LEN IT UP" with a great cry. the cry of a titan. then the dj looks at you, you both make eye contact. then he turns on the attack on titan theme song as you bite your thumb and turn to your full titan form.

all the hoes around are amazed by your ripped body, but this isn't even your final form.

len it up everybody.

A goth who has been part of the subculture since it originally came about, or a goth over the age of 40.

So basically,lenning something up pretty much means using anime pictures during a normal conversation and making things weird.If you decide to len it up,then you are going to be the one who sends anime pictures.