An acronym for Shit I Don't Need, aka junk or
useless stuff. Pronounced
SID-din. Usually used for boating toys and
extra things no one will ever really need.
"Hey
man, did you buy some SIDN yesterday?"
"Yeah dude! I know I don't need it, but it's fun shit!"
"What'd you buy?!"
"An anchor loop, three water chairs, coasters with
extra grip, the third season DVD of Big
Bang Theory, and a cookbook for potatoes!"
"Dude that's some serious SIDN!"