A person can be accused of engaging in hanky-panky when he participates in deceitful activities or improper sexual relations in front of an audience who disapproves of that particular behavior. A person can also be suspected of hanky-panky even if the audience does not actually witness the behavior.
The Merriam-Webster Dictionary defines hanky-panky as "questionable or underhanded activity" or a "sexual dalliance." Although the exact origins of the word are unknown, it was first used around 1841.
There are two possible contexts in which hanky-panky can be used to describe someone's behavior. Firstly, it describes behavior that is simply questionable, as in the sentence, "Joe's card-counting history caused the other poker players to suspect hanky-panky." The hanky-panky in question in this example is the possibility that Joe is counting cards, thus cheating, in the poker game.
Secondly, hanky-panky is used to suggest a sexual dalliance, as in the sentence, "When the two teenagers rushed back inside from the night, their cheeks flushed and their eyes glittered. All of the adults in the room shared a knowing glance with one word unspoken but agreed between them: hanky-panky." In this instance of the word, hanky-panky is detailing possible inappropriate sexual activity that has occurred between the two teenagers.