Source : WordNet®

cos
     n 1: ratio of the adjacent side to the hypotenuse of a
          right-angled triangle [syn: {cosine}]
     2: lettuce with long dark-green leaves in a loosely packed
        elongated head [syn: {cos lettuce}, {romaine}, {romaine
        lettuce}]

Source : Free On-Line Dictionary of Computing

COS
     
        1. {Cray Operating System}.
     
        2. {Corporation for Open Systems}.