(noun), plural form, informal
1. secret or dishonest activity, or scheming
"When money went missing, the members of parliament were accused of financial shenanigans"
2. silly or high-spirited behaviour; mischief
"My toddler always has a special smile when he's been up to his shenanigans"
I usually use shenanigans in the 2nd sense when speaking with my friends! It is almost always used in the plural form.