• harebrained,
• garebrain,
• barebrain,
• narebrain,
• jarebrain,
• uarebrain,
• yarebrain,
• hzrebrain,
• hsrebrain,
• hwrebrain,
• hqrebrain,
• haeebrain,
• hadebrain,
• harrbrain,
• harbrain,
• haerbrain,
• hairbrain,
• harebrane,
• harybrain,
• hayrbrain

• harebrained.

The adjective form of the word "harebrain" is "harebrained".

The plural form of "harebrain" is "harebrains"

The singular form of the word "harebrain" is "harebrain". The word does not change its form in the singular.