The Collaborative International Dictionary of English v.0.48:

Peremptorily \Per"emp*to*ri*ly\, adv.
   In a peremptory manner; absolutely; positively. --Bacon.
   [1913 Webster]

WordNet (r) 3.0 (2006):

peremptorily
    adv 1: in an imperative and commanding manner [syn:
           imperatively, peremptorily]