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When something is so hot that it give you a chubby (partial erection) instantly.
Seeing Jessica Alba in a 2 piece gave me an instachub!
by rMace703 April 16, 2011
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2
When a girl posts a hot picture to Instagram bad you become instantly erect.
Daulton: Dude did you see Ashley’s Instagram picture?

Matthew: Oh my god yes it was so hot it gave me an instachub.
by Lover of instachubs May 23, 2018
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