A Tholian: an example of a non-humanoid lifeform
The term non-humanoid designated lifeforms which did not share certain morphological, biological, and physiological traits with humanoids and could exist in a wide variety of types.
Relations among humanoid species were considered easier than between a humanoid and a non-humanoid one since those lacked a common point of reference to base communications on. (TNG: "The Ensigns of Command")
Animals were considered to be non-humanoid. (TOS: "The Way to Eden") The term "alien" was also sometime used by humanoids to describe non-humanoids. (TNG: "The Child")
A nitrogen sulfide atmosphere was considered an indicator of non-humanoid life. (ENT: "Broken Bow")