Flexibility, pliancy.
The or an act of flexing.
Any flexible insulated electrical wiring.
A point of inflection.
The act of flaunting something; something one considers impressive.
2020, Daniel Varghese, "Aesop's Hand Sanitizer Is a Flex for an Anxious Time", GQ, 6 March 2020
To bend something.
To repeatedly bend one of one's joints.
To move part of the body using one's muscles.
To tighten the muscles for display of size or strength.
(by extension) To flaunt one's superiority.