aftermost

from WordNet (r) 3.0 (2006)

aftermost
    adj 1: located closest to the stern or tail

from The Collaborative International Dictionary of English v.0.48

Aftermost \Aft"er*most\, a. superl. [OE. eftemest, AS.
   [ae]ftemest, akin to Gothic aftumist and aftuma, the last,
   orig. a superlative of of, with the superlative endings -te,
   -me, -st.]
   1. Hindmost; -- opposed to {foremost}.
      [1913 Webster]

   2. (Naut.) Nearest the stern; most aft.
      [1913 Webster]