Here is what the dictionary says:

res·cue ( P ) Pronunciation Key (rsky)
tr.v. res·cued, res·cu·ing, res·cues
To set free, as from danger or imprisonment; save. See Synonyms at save1.
Law. To take from legal custody by force.

n.
An act of rescuing; a deliverance.
Law. Removal from legal custody by force.

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I believe that anyone who comes to the aid of a kitty who otherwise would be miserable, lonely, sick, in harm or caged for most of their life, is a rescuer!