What it means
A tearjerker is a film, book or song so unashamedly sad that it's practically engineered to make you cry, the dying dog, the long goodbye, the swelling music right on cue. You know exactly what it's doing to you and you reach for the tissues anyway. Sometimes you put one on on purpose, just for a good cathartic sob.
Usage examples
"Bring tissues, that film is a complete tearjerker from the first scene."
"She loves a good tearjerker on a rainy Sunday, the sadder the better."
"I wasn't ready for that ending at all, absolute tearjerker stuff."
"We put on a proper tearjerker and ended up crying into the takeaway."
Where it comes from
Recorded in English since the early 1900s, tearjerker grew out of the idea that a story can practically jerk tears out of you. It stuck fast to films, novels, and songs built to hit the soft spot and leave people sniffling in the dark.