not decent; obscene; lustful; unlearned; vile

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

Real definition: 'crude and offensive in a sexual way.'

Definition according to people who watch anime: 'anything remotely sexual.'

What anime fans say when they're vaguely uncomfortable with how they're drooling over 14 year old girls

Slang for smut or pornography.

A lewd is a photograph taking by oneself as a tease. Not a full on nude showing your private parts but teasing the receiver of the photograph.

A picture of a girl in her underwear is considered a lewd.

To lewd a pre-established sfw character is to draw said character in a nsfw setting or position.