1. superlative form of silly; most lacking in good sense or judgment; most foolish
2. superlative form of silly; most playful or lighthearted in a childish way

Examples

• That was the silliest mistake I’ve ever made.
• She told the silliest joke at the party.
• The children were acting their silliest during recess.
• It’s the silliest rule in the entire handbook.
• He wore the silliest hat to get attention.
• That’s the silliest excuse I’ve ever heard.
• The movie had the silliest plot twist.