This article is from the Shenanigans FAQ, by Michael Moncur altshen@REMOVETHIS-starlingtech.com with numerous contributions by others.
A shenanigan is something that is done for no purpose other than to
confuse or fool its intended victim. Shenanigans differ from the
mainstream usage of "practical jokes" or "pranks" in that they are,
above all, harmless. Throwing eggs at someone's car is a prank;
Handing out eggs with odd sayings written on them at a mall is a
shenanigan. I hate to use this example, but most of the things you
see on "TV's Bloopers and Practical Jokes" are shenanigans.
Although there is much overlap between practical jokes, pranks, and
shenanigans, I would like to make this distinction: The victim
responds to a prank by saying, "Damn those kids!" or "I'll get you for
this." (Or by taking legal action.) A shenanigan, on the other hand,
receives a response such as "Why would anyone go to the trouble?" or
"I don't get it." from 'normal' citizens, or is responded to in kind
by a fellow shenaniganist.
In short, if you laugh at it, even if you're the victim... It's
probably a shenanigan. Obviously different people laugh at very
different things, so use your judgement and know your victim.
It should be noted that this is strictly "my" definition of the
term, and any similarity to your definition or the dictionary's is