Katteyomi
Katteyomi (勝手読み) is a Japanese go term referring to subconsciously ignoring good sequences for your opponent during reading, making assumptions that lead to things working out better for yourself. Sometimes known as "wishful reading", it has also been translated as "self-indulgent reading."
As with most Japanese terms, katteyomi is not a mere linguistic curiosity, but describes a very real phenomenon that it is important for go players to be alert to: the psychological tendency to favor yourself in reading out sequences. It's possible that stronger players have developed explicit anti-katteyomi measures, where they consider a positive result a reason to explore alternatives that might be less favorable to themselves.
Katteyomi does not refer to the questionable practice of consciously reading and choosing sequences that you think your opponent is too weak to respond properly to.
Derivation
Katte literally means winning moves(s), from Katsu: to win and Te: move (literally: hand). Yomi is reading. It means to only reading the winning moves instead of considering all possibilities.
John F. No, it has nothing to do with winning. Katte is a very common term in the normal language has several meanings (all written with the same kanji), including "kitchen" and "circumstances". Another meaning is wilfulness/selfishness, or doing something for one's own convenience. That is the one covered by katteyomi. A similar phrase is katteshidai.