Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
I think that the following tags might be synonyms:
competitive-game and strategy (where strategy is the better choice)
path-finding and reachability (with reachability as better choice). Also solvability seems to cover the same concept.
cutting-problem and dissection
image and visual (with visual as better choice)
cryptic-crosswordsletter (occurring only once) and cryptic-crosswords
treasure-hunt and puzzlehunt (with puzzlehunt or puzzle-hunt the better choice)
network and graph-theory (where graph-theory is the better choice)
Looks like all of these have been dealt with by now, except :
network (11 puzzles
and its description even mentions graph theory)
should become a synonym for
graph-theory (58 puzzles).