Adjective used to describe less heavy rock music. Although rock music is generally loud, with a lot of bass and not really "soft", so often confusing as an arguable oxymoron.
I'm listening to some Mamas and the Papas which I guess you could say is "soft rock."
(n) In geology lingo, soft rock is sedimentary rock.
Willie is a soft rock geologist; he only digs shale and stuff.