backsack

Backsack means: The back of the testicles.. It is informal slang, fine in casual speech but not suited to formal contexts. It carries sexual or vulgar connotations; not alarming on its own but worth understanding the context your teen heard it in. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.

backsack means: The back of the testicles.. Register: very informal, often derogatory or vulgar. Avoid in formal, business, academic, or polite writing. Even in casual speech the word can offend and is best left out of a learner's active vocabulary. A common learner mistake is using the word in a register it does not fit, or assuming a single global meaning; native speakers immediately notice when slang appears in formal contexts, so always check the surrounding register before producing it yourself.