noun. A very specific event that was definitely not caused by Matthew McConaughey.
Real citation: "I can't even think. Pretty sure I just had a Robert Downey Jr.-gasm."
(June 13, 2009, Elizabeth Hoag, Twitter, http://twitter.com/riza_a/statuses/2157351573)
Made-up citation: "Many Robert Downey Jr.-gasms were caused by Tropic Thunder, but I dunno about that one where he's a reporter helping a homeless musician. That movie looks so bad, I thought it was another satirical trailer on my Tropic Thunder DVD. I'd rather boil my head and tempura my genitals than watch that."