WordNet sense 1 (a straight segment of a roadway or racecourse):

straight

WordNet sense 2 (performed with little or no delay):

immediate, prompt, quick

WordNet sense 3 (acting or moving or capable of acting or moving quickly):

fast

WordNet sense 4 (without delay or hesitation; with no time intervening):

directly, forthwith, immediately, instantly, now, at once, in real time, like a shot, straight off, right away