waist /weɪst/ noun [C]
B2 the part of the body above and slightly narrower than the hips:
» a small/narrow/tiny/large/thick waist» These trousers are a bit tight around my waist.See picture: waist 
Thesaurus+: ↑The human torso
F0 the part of a piece of clothing that goes around or covers the area between the hips and the ribs:
» The skirt had an elasticated waist.Thesaurus+: ↑Parts of clothes• • •
Extra Examples:» His shirt was open to the waist revealing a very hairy chest.» The veil fell almost to her waist.» I was starting to get a bit flabby around my waist.» She held on tightly to his waist.» She has an impossibly thin waist.