It's wonderful to have a succinct word for a concept like that; I wish there were such a word in English. Do you have any background information about the origins and meaning of this word?
Caneta means pen in portuguese. Canetada, although not a dictionary word, means the act of swiftly using a pen to show "who is the boss" - signing an impromptu decree or order of questionable legitimacy for example.
Portuguese, maybe especially Brazilian Portuguese, has a good number of made-up words that can be created by simply adding certain suffixes to common words. They might not be in the dictionary; that'd grow its number of words exponentially I assume. But they're widely used and understood. In this case, "-ada" is basically added to words when something is used indiscriminately, normally by hitting something or someone, or throwing it.
Whacking someone with a wooden stick ("pau") is a "paulada". Kicking a ball ("bola") on someone is a "bolada". Poking someone with a pin ("alfinete") is a "alfinetada".
Therefore, using a pen ("caneta") indiscriminately becomes a "canetada".
The same word would be used if you threw the pen at someone's head, so there's that.
It's wonderful to have a succinct word for a concept like that; I wish there were such a word in English. Do you have any background information about the origins and meaning of this word?