1. most shabby, worn-out, or in poor condition
Usage: superlative form of ratty
2. most irritable or bad-tempered
Usage: informal; superlative form of ratty

Examples

• He wore his rattiest old jeans to work in the garden.
• The rattiest chair in the waiting room was surprisingly comfortable.
• She donated her rattiest clothes to the charity drive.
• That’s the rattiest excuse I’ve ever heard for being late.
• The dog chose the rattiest blanket as his favorite sleeping spot.
• After three days without sleep, he was at his rattiest mood.