We don't have synonyms for union suits yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are union suit.
(n) :
one-piece underwear, usually long, combining drawers and long-sleeved, button-front undershirt in a single garment, with a flap in the seat that can be opened for defecation.
(n) :
one-piece underwear, usually long, combining drawers and long-sleeved, button-front undershirt in a single garment, with a flap in the seat that can be opened for defecation.