forthwith (prep.)

c. 1200, from forth + with. The Old English equivalent was forð mid. As an adverb, early 14c.

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Definitions of forthwith from WordNet

forthwith (adv.)
without delay or hesitation; with no time intervening;
an official accused of dishonesty should be suspended forthwith
Synonyms: immediately / instantly / straightaway / straight off / directly / now / right away / at once / like a shot