two-piece swimsuit (not a bikini)
Refers to a two-piece swimsuit with more coverage than a bikini, such as a tankini or a set with a top and shorts/skirt. Often used for swimwear that is not as revealing as a bikini.
I'm thinking of buying a two-piece swimsuit this year.
She prefers two-piece swimsuits over bikinis.
Wasei-eigo (Japanese-made English) from 'separate' + 水着 (swimsuit).