What does IRREGULAR mean?

adjective

1. contrary to rule or accepted order or general practice“irregular hiring practices”
2. not occurring at expected times
3. (used of the military) not belonging to or engaged in by regular army forces“irregular troops”
4. (of solids) not having clear dimensions that can be measured; volume must be determined with the principle of liquid displacement
5. falling below the manufacturer's standard“irregular jeans”
6. deviating from normal expectations; somewhat odd, strange, or abnormal“these days large families are atypical”
7. lacking continuity or regularity“an irregular worker”
8. (of a surface or shape); not level or flat or symmetrical“walking was difficult on the irregular cobblestoned surface”