1) Chop-chop 2) Directly 3) Forthwith 4) Hospital stat 5) Immediately 6) In a new york minute 7) Instanter 8) Instantly 9) Medical stat 10) Not later 11) On the double 12) One cat ran off straight away 13) Posthaste 14) Promptly 15) Pronto 16) Quickly 17) Quit standing there 18) Right now 19) Right off 
• (adv.) At once; together.
At·tonce' adverb [ At + once .] At once; together. [ Obsolete] Spenser.