Which word is the past tense of an irregular verb?

1. Hidden
2. Squawked
3. Aimed
4. Tapped

The word "hidden" is the past tense of an irregular verb.

The word that is the past tense of an irregular verb is:

1. Hidden

The past tense of a regular verb is usually formed by adding "-ed" or "-d" to the base form of the verb. However, irregular verbs have their own unique forms in the past tense.

To determine the past tense of an irregular verb, you can consult a verb conjugation list or a dictionary.

Let's analyze the options you provided:
1. "Hidden" - This is the past participle form of the irregular verb "hide." The past tense form is also "hid."
2. "Squawked" - This is the past tense form of the irregular verb "squawk."
3. "Aimed" - This is the past tense form of the irregular verb "aim."
4. "Tapped" - This is the past tense form of the regular verb "tap."

Therefore, among the options given, the word that represents the past tense of an irregular verb is "squawked" (option 2).