instanter

from The Collaborative International Dictionary of English v.0.48

Instanter \In*stan"ter\, adv. [L., vehemently, earnestly. See
   {Instant}, n. & a.]
   Immediately; instantly; at once; as, he left instanter.
   [1913 Webster]

from Bouvier's Law Dictionary, Revised 6th Ed (1856)

INSTANTER. Immediately; presently. This term, it is said, means that the act 
to which it applies, shall be done within twenty-four hours but a doubt has 
been suggested by whom is the account of the hours to be kept, and whether 
the term instanter as applied to the subject-matter may not be more properly 
taken to mean "before, the rising of the court," when the act is to be done 
in court; or, "before the shutting of the office the same night," when the 
act is to be done there. 1 Taunt. R. 343; 6 East, R. 587, n. e; Tidd's Pr. 
3d ed. 508, n.; 3 Chit. Pr. 112. Vide, 3 Burr. 1809; Co. Litt. 157; Styles' 
Register, 452.