1) Amount reducer 2) He who improves a nuisance 3) Legal term 4) One who halts a nuisance 5) Stopper of a nuisance 
• (n.) One who abates a nuisance. • (n.) A person who, without right, enters into a freehold on the death of the last possessor, before the heir or devisee.
A·ba'tor (ȧ*bāt'ẽr) noun (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. 
In law, an abator is someone who abates a nuisance. Formerly, in law, the term
noun a person who abates a nuisance