Top definition
When someone replies to you on Snapchat during a conversation, usually a while later, and you totally forget what you said in the first place.
I sent this girl a dick pic last night, and the next morning she snapchatted me and told me "wow that is small." I had no idea what she was talking about because I had Snap-somnia.
by Ty Does Moose Stuff August 30, 2016