The term "progressive rock" is synonymous with "art rock", "classical rock" (not to be confused with classic rock), and "symphonic rock". Historically, "art rock" has been used to describe at least two related, but distinct, types of rock music. The first is progressive rock as it is generally understood, while the second usage refers to groups who rejected psychedelia and the hippie counterculture in favour of a modernist, avant-garde approach. Similarities between the two terms are that they both describe a mostly British attempt to elevate rock music to new levels of artistic credibility. However, art rock is more likely to have experimental or avant-garde influences. "Prog" was devised in the 1990s as a shorthand term, but later became a transferable adjective, also suggesting a wider palette than that drawn on by the most popular 1970s bands.