Someone who hangsout a lot with a couple and is sexually interested in one or more people in that already existing relationship.
T: "Don't you think it's weird how much Natasha is hanging out with Bucky and Steve? Doesn't she get tired of the Thirdwheeling?
L: "Nah she has been crushing on both of them for months. She's a Thirstwheel."
L: "Nah she has been crushing on both of them for months. She's a Thirstwheel."
by Glitterpussy120 June 11, 2018
Get the Thirstwheelmug.