According to jisho.org it means "hands and feet; limbs". But can it mean one limb (an arm or a leg)? I looked in Daijisen, and there I see 手と足. So it seems like it's arms and legs, not arms or legs.
Then I looked at jisho.org for "limb," and found there 枝. Which I looked in Daijisen, and one of the meanings was 人間や獣の手足.
So which is it? Arms and legs? Or an arm or a leg (possibly in the plural)?
Usually, 手足 generically refers to the four limbs, such as in 手足を伸ばす ("to stretch out"). If you want to say "a limb" referring to one specific person, you usually have to say 手か足, not 手足. However, 手足 sometimes means "arm or leg" when many unspecified people are involved. For example, when you say something like 戦争で多くの人が手足に障害を受けた, this means that many people are impaired in one or a few of their limbs, not all four.
At least in modern Japanese, 枝 never refers to limbs. If it's in a dictionary, it's an obsolete meaning no one uses anymore. However, in medical, biological or legal contexts, we use 肢【し】 (note the left radical, which is this). For example, 四肢【しし】 is a stilted and technical alternative of 手足, and 上肢【じょうし】 is a medical term for "upper extremities". In highly medical contexts, 肢 can be used alone to refer to "(a) limb", but this should be avoided in ordinary conversation.
