1. A person's buttocks.
Usage: informal; slang; often used by or around children

Examples

• The child fell on his heinie while playing in the park.
• She slipped on the ice and landed on her heinie.
• The toddler was running around showing off his heinie.
• He got a spanking on the heinie for misbehaving.
• The baby's heinie was sore from the diaper rash.