A ridesharing arrangement in which people travel together. (noun)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "rideshare" in a sentence
"Phoenix: more than 40 percent of staff share the ride instead of driving alone by offering a 100 percent bus subsidy, walk / bike subsidies of $5 per day, prize drawings and free days off for those who "rideshare" for 90 days or more."
"Hitchhiking may be dead, but the Craigslist rideshare board is thriving."
"For businesses operating within and drawing their workforce from areas like greater Atlanta that are plagued by choking traffic and long commute times, the Enterprise rideshare program is a ready-made vanpool solution that helps make for happier employees, increased productivity, and reduced costs for both workers and employers."