Well, one poly person I knew called his other lovers "sweeties." Seems to be a useful term.
I've got a gf, but the other 2 guys I am presently seeing, I call sweeties.
I shy away from that "other husband," or "other wife" term, b/c of when my ex met his sweetie, he imm wanted to make her a wife in our home, before I was ready. He moved way too fast for my comfort. Esp since we'd been together and mono 20 yrs at that point. No way was I comfy letting her gain wife status so quickly.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
Mags (poly, F, 61) loving miss pixi (poly, F, 39) since January 2009, living together since 2013
"Master," (mono, 36), miss pixi's Dom for 3 years