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!
by ICantThinkOfAUsername June 21, 2015
Get the Neville Longbottom mug.
The best person in Harry Potter. He full on stands up to Lord Voldemort in the last one. And your just like HELL YEAH!
Puberty also made him hot.
Person 1: DAAAAYUUUM, WHO'S DAT?
Person 2: Oh that brave hottie is Neville Longbottom
by strawberiiya July 30, 2011
Get the Neville Longbottom mug.
(n)

A forgetful, goofy wizard who became rebellious and bad-ass (see BAMF). A fellow Gryffindor in Harry's year (see Harry Potter), Neville used to be shy, friendless, tearful, forgetful, and a bit of a loser.
However, in Harry Potter and the Deathly Hallows, Neville became one of the most BAMFW (Bad Ass Mother Fucker Wizards) in the world. :)
B.A.M.F. moments of Neville Longbottom, in "Deathly Hallows":

1. He killed Nagini, Voldemort's snake, with the Gryffindor sword, whilst his head was on fire.
2. He stood up to Voldemort, saying boldly he wouldn't join them until 'Hell freezes over'.

3. He stood up to the Carrows, asking them how much Muggle blood they've got.
4. He kept recruiting Dumbledore's Army even after Harry, Ron and Hermione had left.
by Average_jo October 26, 2009
Get the Neville Longbottom mug.
One of Harry's fellow Gryffindor's - and a member of his class. His parents got tortured over and over again by a Death Eater using the Cruatious curse - until they permananently lost their minds.

A sad and lonely individual who hasn't lived up to their potential yet.
Why are you acting like Neville Longbottom?
by Some stuff July 19, 2006
Get the Neville Longbottom mug.
When a non-attractive person goes through puberty and becomes very attractive as a result.

First seen on Tumblr and Imgur, this term refers to Matthew Lewis's battle and victory over puberty.
"Have you seen Lisa since grade school?"
"No I have not, she really Neville Longbottomed. Damn."

"I was staying at my friend's house when her brother who I haven't seen in years walks in to say hello. I was in shock, as he Neville Longbottomed."
by Jamie McCrimmon August 22, 2013
Get the Neville Longbottomed mug.
BAMF.
Neville surprised us in the seventh Harry Potter by being such a badass. We now like to refer to him as BAMF. If he lets us.
Shall we review?

"Harry heard a scuffle and a shout, then another bang, a flash of light and a grunt of pain; he opened his eyes an infinitesimal ammount. Someone had broken free of the crowd and charged at Voldemort."
This badass would be Neville.

"The longer Harry looked at Neville, the worse he appeared: one of his eyes was swollen, yellow and purple, there were gouge marks on his face, and his general air of unkemptness suggested that he had been living rough. Nevertheless, his battered visage shone with happiness as he let go of Hermione and said again, 'I knew you'd come! Kept telling Seamus it was a matter of time!'
'Neville what happened to you?'
'What? this?' Neville dismissed his injuries with a shake of the head. 'This is nothing.'"

Finally the most BAMF moment of all:
"In one swift, fluid motion Neville broke free of the Body-Bind Curse upon him; the flaming Hat fell off him and he drew from its depths something silver, with a glittering, rubied handle-
The slash of the silver blade could not be heard over the roar of the oncoming crowd, or the sounds of the clashing giants, or of the stampeding centaurs, and yet it seemed to draw every eye. With a single stroke, Neville sliced off the great snake's head, which spun high into the air, gleaming in the light flooding from the Entrance Hall, and Voldemort's mouth was open in a scream of fury that nobody could hear, and the snakes body thudded to the ground at his feet-"
BAMF!
"If you're looking for Neville on the Marauder's map, he's labeled 'BAMF.'"

"Neville uses Nagini's blood as soy sauce."

"Neville Longbottom is what's beyond the veil."
by mathilde August 19, 2007
Get the neville longbottom mug.
a kid who seems like a loser who is scared of his granny, but later in the series he becomes more of a bamf. we find out that his parents were bamfs. he hooks up with harry potter's girl before harry potter. he becomes a genius at growing herbs and plants. and he kills voldemort's snake
neville longbottom is the american dream of bamf-erry except that he's british
by too many names are used April 18, 2011
Get the neville longbottom mug.