abator

from WordNet (r) 3.0 (2006)

abator
    n 1: a person who abates a nuisance

from The Collaborative International Dictionary of English v.0.48

Abator \A*ba"tor\ ([.a]*b[=a]t"[~e]r), n. (Law)
   (a) One who abates a nuisance.
   (b) A person who, without right, enters into a freehold on
       the death of the last possessor, before the heir or
       devisee. --Blackstone.
       [1913 Webster]

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

ABATOR is, 1st, he who abates or prostrates a nuisance; 2, he who having no
right of entry, gets possession of the freehold to the prejudice of an heir
or devisee, after the time when the ancestor died, and before the heir or
devisee enters.  See article Abatement. Litt. Sec.  897; Perk. Sec.  383; 1
Inst. 271; 2 Prest. Abst. 296. 300. As to the consequences of an abator
dying in possession, See Adams' Eject. 43.