What part of speech is regularise?

Regularise can be categorized as a verb.

Parts of speech

1. regularise is a verb, present, 1st person singular of regularise (infinitive).
2. regularise is a verb (infinitive).

Verb
regularise - bring into conformity with rules or principles or usage; impose regulations; "We cannot regulate the way people dress"; "This town likes to regulate"
regularise - make regular or more regular; "regularize the heart beat with a pace maker"