Elasticated (adjective)
Of clothing or part of a garment, containing a strip or strips of elastic, especially in the waistband, cuffs or the ends of the legs, in order to make the clothing fit snugly.
“an elasticated jacket”
“slacks with an elasticated waistband”
Elasticized (verb)
simple past tense and past participle of elasticize
Wiktionary
Elasticated (adjective)
(of a garment or material) made elastic by the insertion of rubber thread or tape
“trousers with elasticated waists”
Oxford Dictionary