Definition of "flex"
flex
/flɛks/
noun
countable and uncountable, plural flexes
(uncountable) Flexibility, pliancy.
(uncountable, chiefly Britain) Any flexible insulated electrical wiring.
(countable, geometry) A point of inflection.
verb
third-person singular simple present flexes, present participle flexing, simple past and past participle flexed
(intransitive, slang, by extension) To flaunt one's superiority.