Onenighter, a slang term for a one-night stand, can be substituted for a number of different words and phrases. "Casual hookup" is a common term used to describe a similar encounter, while "fling" or "romp" could also be used. Another option is to use a more straightforward phrase like "one-time sexual relationship." For a more playful descriptor, "wham-bam-thank-you-ma'am" can convey the same meaning. Ultimately, it's important to remember that the language used to describe sexual encounters should be respectful and consensual, and that there are a wide variety of terms that can be used to appropriately describe these experiences.