1. slang Behaving in an erratic or unpleasant manner. Oh man, he's really illin'—I have no idea why he just stormed out of here.
2. slang Unhappy. A: "Why's she illin' today?" B: "Well, it looks like she got an F on her psych paper. I bet that has something to do with it."
3. slang Sick or unwell. I was illin' last week, that's why I was absent.
1. mod. being ill; being sick. She was illin’ big time and could not come to class.
2. mod. ill-behaved. You are most illin’ and you are bugging me, Kim. Stop it!
3. in. behaving badly. Stop illin’ and pay attention.
4. mod. upset. What are you illin’ about? Everything is ice.
5. Go to ill.