Antonyms of adj helical

1 sense of helical

Sense 1
coiling, helical, spiral, spiraling, volute, voluted, whorled, turbinate -- (in the shape of a coil)

INDIRECT (VIA coiled) -> uncoiled, straight -- (no longer coiled)

Similarity of adj helical

1 sense of helical

Sense 1
coiling, helical, spiral, spiraling, volute, voluted, whorled, turbinate -- (in the shape of a coil)
       => coiled (vs. uncoiled) -- (curled or wound (especially in concentric rings or spirals); "a coiled snake ready to strike"; "the rope lay coiled on the deck")