In a right triangle, T, with a hypotenuse c, and katheten of a and b, with verticies meeting at angles α, β, and γ (where γ is π radians (90 degrees (no one really cares about degrees))),

             | \
             |  \ 
          b  |   \ c
             |    \
             |     \
            γ        β  

           Ankathete      a
cos(α) =  ------------ = ---
           Hypotenuse     c

          Gegenkathete    a
tan(α) =  ------------ = ---
            Ankathete     b

It is used almost exclusively in German trigonometry, and I assume it means "Adjacent Leg", although like the word "hypotenuse", it has Greek origins. Strangely, kathete has been dropped from the majority of western trigonometry.

00100 confirms the translation of this to "Adjacent Leg". Thanks!