上劲 is a separable verb (离合词) meaning 'to get into it' or 'to do something with gusto' — putting real energy and enthusiasm into an activity. It often appears in the pattern 上…劲, where a measure word or adjective can slot between the syllables, like 上什么劲 ('what's the point of trying so hard?') or 上大劲 ('put in a lot of effort'). You can use it for work, study, games, or arguments — any situation where someone is really going for it.