Choshi ga ii, or good choshi is generic Japanese which can also be applied to go, and translates as something likefiring on all cylinders, in the groove.
I also recalled that I've used impetus, and another way of looking at it is that a choshi move creates a cascade effect[2].
choshi ii would (in go) presumably mean, the game is going well for sid player, or if used about a player, s/he is winning a large amount of games/playing well.