1. Something so ridiculous that it's par with the outrageousnesss of a Tijuana donkey show; a situation or circumstance that is beyond redonkulous.
2. A well-endowed man who's cock is as large as a donkey's, making copulation difficult or challenging.
1. - You’re not going to believe this! My ex-boyfriend dumped me because I wanted kids and he didn't - and now that he wants kids, he can't - he found out he's sterile!
- No way! That’s Tijuana redonkulous!
2. God that guy was Tijuana redonkulous - it took an entire tube of KY to get him in me and now my pussy resembles a Star Gate.
Contrary to whatever your reading the original word came from modern poker. The word is a combination of the 2 root words "Ridiculous" and "Donkey". The ridiculous comes for the bad judgment at a poker table and the Donkey is what poker players call other poker players that apply bad judgment. Hence "redonkulous" ridiculous donkey.
Why would call that bet with a 3 outer? That's redonkulous.