How do you say threesome in hebrew?

Answer 1

שלישיה, or with Nikkud (vowel marks): שְׁלִישִׁיָּה
"Shlishiyah" (pronounced: shli-shi-yA)

You can go on with it forever with "revi'iyah" (a group of four), "chamishiyah" (a group of five), "shishiyah" (a group of six), "shvi'iyah" (a group of seven), "me'iyah" (a group of hundred), "alpiyah" (a group of thousand) etc...

Answer 2

i don't think there's a way to say it in one word, but you could say "k'vutzah shel shalosh/shlosha" which is "a group of three feminine/masculine." good luck!