Go stag
Definition 1 of 1
Pro Tip 1/3Colloquial Use
The phrase is casual and commonly used in everyday conversation, not in formal writing. 
Hey, are you going stag to the office party next week?
Pro Tip 2/3Event Specific
Mostly used for events where couples are the norm, like dances, weddings, or formal parties. 
When Jessica mentioned she'd go stag to her cousin's wedding, her mother was surprised.
Pro Tip 3/3Gender Neutral
Although historically male-oriented, it's now used for anyone attending an event alone. 
Even though the invitation allowed a plus one, Sara chose to go stag to the gala.