Most negative stiffness metamaterials exhibit negative stiffness effects in only one direction. Herein, based on the theory of anisotropy, the concept of “negative stiffness” is redefined. A method to determine whether a material has all‐directional negative stiffness is proposed. The possibility and difficulty of achieving all‐directional negative stiffness are discussed. A new type of negative stiffness metamaterial comprising negative stiffness rotation hinges and rigid trusses is studied. The results show that quasi‐all‐directional negative stiffness is achievable.