What is an irregular verb?
To explain what an irregular verb is, I will start with defining a regular verb.
A regular verb has Past Simple and Past Participle forms created by adding "-ed" suffix to the infinitive form.
play - played -played
cry - cried - cried
visit - visited - visited
and so on.
A verb is irregular if it is not regular. It may create Past Simple and Past Participle forms in many ways:
All 3 forms different: examples: see - saw - seen, go - went - gone, etc.
Past Simple and Past Participle forms the same, but different from infinitive: buy - bought - bought, get - got - got, sell - sold - sold, etc.
All forms the same: cost - cost - cost, hurt - hurt - hurt, cut - cut - cut etc.