- any of various classes (esp. Bryopsida) of very small, green bryophytes having stems with leaflike structures and growing in velvety clusters on rocks, trees, moist ground, etc.
- a growth of these
- any of various similar plants, as some lichens and algae
Origin of mossMiddle English mos, a bog, moss from OE, a swamp, akin to Old Norse mosi, German moos, a bog, moss from Indo-European an unverified form meus- (from source Classical Latin muscus, moss) from base an unverified form meu-, moist