To bend your knees and lower yourself so that you are close to the ground and leaning forward slightly. (Cambridge Dictionary)
Adopt a position where the knees are bent and the upper body is brought forward and down, typically in order to avoid detection or to defend oneself. (Oxford Dictionaries)
A crouching stance or posture. (Oxford Dictionaries)
To lower the body stance especially by bending the legs. (Merriam – Webster)
To lie close to the ground with the legs bent. (Merriam – Webster)
If you are crouching, your legs are bent under you so that you are close to the ground and leaning forward slightly. (Collins Dictionary)
If you crouch over something, you bend over it so that you are very near to it. (Collins Dictionary)
Thesaurus plus. Crouch and Hunch.