monokini

noun2

1. •
   A one-piece swimsuit, which may cover both the chest and the crotch (as contrasted with a bikini, which consists of two pieces).

   • [Psylocke is] wearing a mix between a monokini and cut-out swimwear, a wardrobe change[.] — 2014
2. •
   The lower part of a bikini without the upper part (i.e., topless).

   • In fact, the San Francisco Chronicle featured a photo of a woman in a monokini — her exposed breasts clearly visible — on its front page. — 2016