Closest meaning words are words which are most alike.

Example: Think about these three words: tall, big and large. Which two are CLOSEST in meaning? big and large are closer than tall and big or tall and large. Tall means big only in terms of how high something is. 

big, large
big, mean
rest, large
small, large
Answer: big, large
big, large is the correct answer because big and large mean the same thing, of considerable size, and the others are unrelated."