The Brief: Netflix and Chill refers to a invitation to hook-up, disguised as a casual movie night.

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Asking someone over to “Netflix and Chill” is a less-direct way of inviting them over for a hook-up. The invitation is often solicited when someone is thirsty, and sent via sexting or by sliding into someone’s DM’s.
The first recorded use of the phrase “Netflix and chill” was in a Twitter post by user @NoFaceNina in 2009.
I'm about to log onto Netflix and chill for the rest of the night.
— NoFaceNina (@nofacenina) January 22, 2009
The meaning has since evolved to have a much more sexually explicit connotation.
My 8 year old son just asked his grandma "Netflix and chill?" and I might have just died.
— Ely (@elyeathea) February 17, 2019
Today, the phrase, “Netflix and Chill” means to watch Netflix with a romantic prospect, with the expectation of it leading to sexual activity. The phrase is almost exclusively associated with casual sexual encounters, like friends with benefits or situationships.
I just met a Becky in the Hills.
Said she wanna Netflix and chill.
She told me that her love is real.-Yung Tory, “Netflix and Chill”
Various music artists, including Yung Tory, Drake, and Kap G, have incorporated the phrase into their songs.