A "practical joke" or show of bromantic affection where a guy jumps on the back of an unsuspecting guy and grabs that guy's genitals/penis (i.e. the unicorn's horn).
"Wow, I was just in the lobby and saw a drunk guy jump on another dude's back and grab his junk! He unicorn ambushed him in front of everyone!"
by Hola Gatino! October 14, 2008
A sign of bromantic affection or a practical joke where a guy jumps on the back of an unsuspecting guy and grabs his family jewels so hard he defecates in his pants!
"Dude! I was down in the lobby and just saw a big guy just jump on this AZN dude's back and grab his nuts! The AZN was so freakin scared he shit his pants!"
"No way! He Unicorn Ambushed that slope!"
"No way! He Unicorn Ambushed that slope!"
by Gatito! November 19, 2008