1. past tense of fink; to inform on or betray someone, especially to an authority or rival
Usage: informal; often used with 'on'
2. past tense of fink; to fail to fulfill a promise or obligation; to back out
Usage: informal; often used with 'out'

Examples

• He finked on his friends to avoid getting in trouble.
• She finked out of the agreement at the last minute.
• The witness finked to the police about the crime.
• They felt betrayed when he finked on the group.
• He finked out of helping us move.
• The informant finked on the operation to the authorities.