This has been bothering me all day. I'm having that problem where a specific word just disappears from your vocabulary for whatever reason. Google is incredibly unhelpful.
The word is used when two specific pieces of information don't seem to add up, or you're not sure how to piece them together, and it's used in a context like this: "I'm not sure how to [x] this new information with what we already know."
Another use would be when someone says two different things that seem contradictory: "I don't know how to [x] his latest statement with his original speech or supposed goals."