A game of chance, played by betting on the outcome of two pennies thrown in the air.(noun)
Having two document pages per printed page.(adjective)
With two people aboard.(adverb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "two-up" in a sentence
"Arctic Cat has many different two-up models to choose from, but the TRV 1000 cruiser is the deluxe, has-it-all, comes-with-everything model."
"The most versatile two-up ATV ever, the X2 has a passenger seat that folds up and out of the way to create a 400-pound capacity deep-sided dump box in just seconds."
"Despite the economic situation, the two-up category continues to grow, out-pacing the ATV industry."