To Meld - What does "to meld" mean?

from Volokh Conspiracy:
And like me, did you “learn” the meaning from the Vulcan mind-meld? (Continuing a discussion with Michelle from comments to an earlier post.) I have to say, I did “learn” the word by hearing its repeated use on Star Trek. To meld, so far as I’ve ever been concerned, means ... whatever it is that Spock did with his mind. Feel free, Oh Ye Prescriptivists, to correct me in the comments.