1. superlative form of grey; having the most grey color or shade
Usage: superlative degree; also spelled 'grayest' in U.S. English
2. superlative form of grey; most dull, gloomy, or depressing in mood or appearance
Usage: figurative use

Examples

• The greyest clouds hung over the city all morning.
• Of all the paint samples, this one is the greyest.
• That was the greyest day of the entire winter.
• The greyest part of the fabric had faded from washing.
• She wore her greyest sweater on the coldest day.
• The greyest skies often bring the most rain.