Equivocator is someone who is ambitious or never tell the whole truth.

‘Faith, here’s an equivocator, that could
swear in both the scales against either scale;
who committed treason enough for God’s sake,
yet could not equivocate to heaven: O, come
in, equivocator.’ by Porter.

Porter thought that Macbeth was knocking the door and and called him an equivocator because he is so ambitious and never tell the whole truth about the part where King Duncan was killed. The mataphor ‘The scales against either scale’ means something about balance.