strapless

 Longman Dictionary of Contemporary English 5++朗文当代英语 5++LDOCE 5++朗文 5++strap·less /ˈstræpləs/ adjective  strapless dress/gown/bra DCCone that does not have straps over the shoulders 无肩带连衣裙/礼服/胸罩

Examples from the Corpus

strapless• The black taffeta silk ballgown was strapless and backless with a plunging, gravity-defying decolletage.• I saw a strapless black gown in the corner, a pair of stilettos discreetly hidden on the floor.• Susanna wore a black silk strapless dress.• I had a little dress made - it was a strapless taffeta number, very girly and aqua blue.

strap·less adjectiveChineseSyllable  

one straps over not Corpus have that does

strapless
strap‧less /ˈstræpləs/ adjective
strapless dress/gown/bra one that does not have straps over the shoulders

strap·lessBrE /ˈstræpləs/ 🔊NAmE /ˈstræpləs/ 🔊 adjective(especially of a dress or bra 尤指连衣裙或胸罩) without straps 无肩带的；无吊带的