The torso or trunk was the central part of one's body.
In 2368, Doctor Beverly Crusher described a proposed course of treatment for Worf's spinal injury, in which neural transducers would be implanted in the Klingon's lower torso and legs. (TNG: "Ethics")
In 2380, Beckett Mariner would describe Shaxs as having "a giant torso and little hands." (LD: "Second Contact")
When conversing with the severed head of Data from a purple alternate reality in 2382, Tendi was free to ask any questions she wanted as long as it did not require hands, feet, or torso for him to answer. (LD: "Fully Dilated")
In 3189, an atomic scan of Philippa Georgiou's musculoskeletal system revealed that the lean mass of her trunk was 19.9 kilograms (kg). (DIS: "The Sanctuary")