Antonyms of adj high-strung

1 sense of high-strung

Sense 1
edgy, high-strung, highly strung, jittery, jumpy, nervy, overstrung, restive, uptight -- (being in a tense state)

INDIRECT (VIA tense) -> relaxed -- (without strain or anxiety; "gave the impression of being quite relaxed"; "a relaxed and informal discussion")

Similarity of adj high-strung

1 sense of high-strung

Sense 1
edgy, high-strung, highly strung, jittery, jumpy, nervy, overstrung, restive, uptight -- (being in a tense state)
       => tense (vs. relaxed) -- (in or of a state of physical or nervous tension)