Wiktionary
alt. A beard growth visible late in the day on a man whose face was clean-shaven in the morning. n. A beard growth visible late in the day on a man whose face was clean-shaven in the morning.
Wikipedia
Five O'Clock Shadow is an a cappella group from Boston, Massachusetts, that has been in existence since 1991. The band has performed on FOX News, A&E Network, ABC, ESPN and VH-1's "breakthrough" series. They have released 4 cassettes and 6 CDs, winning many Contemporary A Cappella Recording Awards.
The group has toured with many famous acts including The Boston Pops, Aaron Neville, Edwin McCain, Patty LaBelle, Kool and the Gang, Blessed Union of Souls and James Brown.
Usage examples of "five o'clock shadow".
A tall, lean man, with an unremarkable face and a permanent five o'clock shadow, he was, like a number of men who are humourless and unaware of it, given to smiling at frequent intervals and usually at inappropriate moments.
He scrubbed a hand over his jaw, five o'clock shadow rasping his rough palm.
Thirty-nine years old, with thinning hair, thick-lensed spectacles, a five o'clock shadow and a taste for plaid short-sleeved shirts.