To get overly excited or overly confident about something.
Kid: "Dad, can we get movie theater-butter popcorn? It's 2 for $5."
Dad: "Oh what the hell, why not..."
Kid: "Really!? You really mean it!?"
Dad: "Calm down, calm down... don't get a big DICK!"
"Bobby got that girls number so now he keeps getting a big dick about it."