1. A patronizing or mocking expression of sympathy, often used to tease someone for complaining about something trivial.
Usage: informal; chiefly British; often used in a condescending tone

Examples

• He complained about the cold, and she said, 'Diddums, did someone forget their jacket?'
• When the child whined about losing the game, the older sibling teased, 'Diddums, better luck next time.'
• She mocked his minor inconvenience with a sarcastic 'Diddums' and a smirk.
• The coach responded to the player's excuse with 'Diddums, everyone's tired.'
• He used 'diddums' to mock his friend's complaint about the restaurant being crowded.