Yes, well its more general sense is simply "to cut off," as your quoted verses show. Now there's no disputing that ἀποκόπτω can be translated as "to castrate or make a eunuch," and it is in some places outside the NT. So this would be a valid translation if the context were to fit. But now, that's the question.
The fuller passage reads:
"For in Jesus Christ neither circumcision avails any thing, nor uncircumcision; but faith which works by love. Ye did run well; who did hinder you that ye should not obey the truth? This persuasion cometh not of him that calls you. A little leaven leavens the whole lump. I have confidence in you through the Lord, that ye will be none otherwise minded: but he that troubles you shall bear his judgment, whosoever he be. And I, brethren, if I yet preach circumcision, why do I yet suffer persecution? then is the offense of the cross ceased. I would they were even cut off which trouble you." (Galatians 5:6-12)
The words "you" in this passage are all in plural, which means he was addressing them as a congregation, not individually. And his desire was that a little leaven not leaven the whole lump. So he was expressing his desire that they be cut off from the congregation before they did (notice that the KJV here translates the middle as transitive and passive, meaning he wished others would "cut them off," not that they would cut themselves off. So if the meaning here is "castrate," then he would have been saying "I wish someone would castrate them," which is not only a pretty rough command to carry out in real life with grown men, but also a really harsh sentence even on a heretic, LoL. :) ).
Anyway, he was really just saying he hoped they be cut off from the congregation altogether before they corrupted it. The allusion to circumcision here may or may not even itself be present.