Generally, shrank is the simple past tense form of "shrink" like in "I shrank the shirt in the wash." Shrunk is the past participle being paired with "have" as in "I have shrunk the jeans." There are rarer examples of shrinked and shrunken in literature but not enough to support those usages as standard.

What does it mean to be shrunk?

shrink. / (ʃrɪŋk) / verb shrinks, shrinking, shrank, shrunk, shrunk or shrunken. to contract or cause to contract as from wetness, heat, cold, etc. to become or cause to become smaller in size.

What does shrunk shrank mean?

shrunk or shrank

To shrink means to become smaller. Shrank is the past tense, and shrunk is the past participle.