What does "red-letter" mean?

To mark or strike with red letters (a person or an object) for particular attention.

What is a synonym for "red-letter"?

Common synonyms include: memorable, notable, noteworthy, observable, rubric, special.

adj, verb

adj, verb ·Rare ·Advanced level

Verb

1
To mark or strike with red letters (a person or an object) for particular attention. transitive

Adjective

Adjective

"July 4th is a red-letter day in America."