A child is talking to another child:
"Hey! Guess what animal it is. It is white and black and has a long neck."
"Hey! Guess the animal. It is white and black and has a long neck."
Which one is correct?
They are both correct, but the word guess is used in different senses:
The examples given are more enlightening than the definitions; you see that the usage of guess is correct either like this:
or like this: