To hitchhike means to travel by getting free rides from passing cars, usually by standing at the roadside and signaling drivers with your thumb pointed up. Before highways had rest stops and when fewer people owned cars, hitchhiking was a common way to travel long distances. A person hitchhiking is called a hitchhiker.

The practice works on an informal agreement: the driver offers free transportation, and the hitchhiker provides company or sometimes helps with gas money. During the 1960s and 1970s, hitchhiking was especially popular with young travelers exploring the country. Today it's much less common, since many people consider it unsafe to accept rides from strangers.

The word can also mean joining onto something else without permission or effort. A seed might hitchhike on your sock during a nature walk, traveling to a new location without doing any work. In science, small organisms sometimes hitchhike on larger animals, getting transported to places they couldn't reach on their own.

When someone gets a hitchhiking ride, they're getting somewhere by relying on another person's vehicle and goodwill rather than their own transportation.