1. Contrary to rule, accepted order, or general practice: irregular hiring practices.

2. Not conforming to legality, moral law, or social convention: an irregular marriage.

3. Not straight, uniform, or symmetrical: irregular facial features.

4. Of uneven rate, occurrence, or duration: an irregular heartbeat.

5. Deviating from a type; atypical.

6. Botany Having differing floral parts, as of a zygomorphic or asymmetric flower.

7. Falling below the manufacturer's standard or usual specifications; imperfect.

8. Grammar Departing from the usual pattern of inflection, derivation, or word formation, as the present forms of the verb be or the plural noun children.

9. Not belonging to a permanent, organized military force: irregular troops.

1. One, such as an item of merchandise, that is irregular.

2. A soldier, such as a guerrilla, who is not a member of a regular military force.