Meaning

• 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"

Meaning

• 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.