Definition of elastic:
(adj) :
capable of
stretching; particularly, capable of stretching so as to return to an original shape or size when
force is released; made of elastic
"the rope is somewhat elastic, so expect it to give when you pull on it."
(n) :
an elastic material used in clothing, particularly in waistbands and cuffs; an
elastic band
"running shorts use elastic to eliminate the need for a belt."