1.verbTo try to get a ride in a passing vehicle while standing at the side of a road, generally by either sticking out one's finger or thumb or holding a sign with one's stated destination.
2.verbTo be carried along with something else, for example Genetic Hitchhiking where a gene is propagated because it occurs in conjunction with a favourable mutation, or Cultural Hitchhiking where a cultural trait spreads with a technologically advanced population.