69

Full definition of 69

(plural 69s)

1990, Ivan Stang, Three-fisted tales of "Bob": short stories in the subgenius mythos, They spent all day in their room, injecting and 69ing, injecting and 69ing.
2013, Mark Titus, Don't Put Me in Coach, if the Bananas in Pajamas would have somehow teleported themselves to our arena, walked out to midcourt, started 69ing, and then finished each other off with a couple rusty trombones before sprouting wings and flying away...