(noun, vulgar slang): an established lesbian or bisexual woman who helps a bicurious woman or girl awaken a lesbian attraction by way of sexual experimenting.
After a weekend with Charlene the tuna helper, Stacy knew for sure that she was a lesbian.
from "tuna" (often used to describe the smell of human female genitalia), and "helper" (one who helps)
This is based on the use of the "stranger" where the male lays on his own arm to put it to sleep. Then uses his own arm to masturbate himself but here's the twist...
Put the arm to sleep with two fingers extended and have your female partner use your stranger hand to finger her vagina to her satisfaction.
To take something small, that doesn't quite qualify as a theft. Probably from the Danish "skæv" or the Dutch "scheef", both of which are pronounced similarly, meaning "askew, or not quite right'. To change an item's ownership without permission, but only something small and of little worth.
"I skeefed an apple off the neighbor's tree." "I skeefed some chips outta your bag when you looked away." "Don't skeef my chair when I go to the bathroom."