Definition of "flex" []

• To bend (something pliant or elastic). (verb-transitive)
• To bend (a joint). (verb-transitive)
• To bend (a joint) repeatedly. (verb-transitive)
• To contract (a muscle, for example). (verb-transitive)
• To move by muscular control: "Sandy flexes his brow characteristically” ( Scott Turow). (verb-transitive)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "CLANCY: And it's a whole industry, because you've to have your cars -- in Brazil, you find most of the cars are what they call flex vehicles, so they can either run on ethanol, or they can run on regular unleaded gas."
• "If you wanted all this dynamic html content you should have went with adobe flash (flex is da bomb)."
• "They run deeper than Rules, allow for a bit of flex (let's face it, there isn't a Rule for every situation and sometimes flex is needed to allow for times when you need to bend one place to keep something more important intact), but still provide some boundaries, a compass for making good choices."