A slang word usually used in yaoi (male/male intimate relationships) culture, made by combining the Japanese terms "seme" (the dominant one) and "uke" (the submissive one). It describes a person that enjoys both positions in a relationship and moves between the two based on his mood, the mood of his partner, and the situation itself.
As he didn't like limiting his options and found both positions enjoyable, he preferred the fickle nature of the label "seke".
It means you can either be uke or seme in a male/male "relationship"... Uke meaning submissive, seme meaning dominant...
My brother's seke in his relationships...it depends on who's taller...