To get
significantly more attractive after going through the process of puberty.
Origin stems from
Harry Potter, where the character Neville Longbottom (actor:
Matthew Lewis) went from a dumpling shaped (but very sweet) 11 year-old to a daaaamn fine (and still very sweet) 25 year-old today.
The word was popularised by tumblr usage as both a noun and a verb.
Me
looking in the mirror: I'd better Neville Longbottom by the time I get to uni, or I'm going to die alone. :/
Person returning home from uni: Is that...? Is that Susan?! Well she certainly
Neville Longbottomed.
Person referring to their boyfriend: Nah, I'm not gonna break up with him. Yeah he's kinda pudgy, bit
fingers crossed he'll do a Neville Longbottom!