jesus christ. 'Wanna sesh' is a term coined boy 14-year-old frat boy wannabes who will likely end up in waste management as a profession. The term is short for "do you want to have a session" or "do you want to hang out," but rest assured that it can and will be used in any way greasy middle school boys see fit. Soon, this phrase will enter the slang-waste land accompanied by "Swagyolo" and "fucking A," but the day will not come soon enough

A jack off buddy (from 'cum' /'come', meaning 'semen', and 'companion'); a friend that you get together with for sessions of solo or mutual masturbation
Variant of: cumpanion (from 'companion' & 'cum'); jack off buddy & wank bud & JO buddy
Similar to: fuck buddy