The part of the day from noon or lunchtime until sunset, evening, or suppertime or 6pm.
The later part of anything, often with implications of decline.
A party or social event held in the afternoon.
one day of solar time, the time between successive noons; the time in which a planet such as Earth apparently rotates once around its axis, relative to the sun (on Earth about 24 hours as an average - the length of solar day is not constant throughout the year)