From im- + measured. immeasured (comparative more immeasured, superlative most immeasured) that has not been measured; huge, enormous 1590, Edmund Spenser...
Bright Scolopendraes, arm'd with siluer scales, / Mighty Monoceroses, with immeasured tayles. A centipede of the genus Scolopendra. 1845 November, The Eclectic...