That does not labour; not requiring or characterized by hard work, effort, or exertion.
Early 17th century; earliest use found in James Sempill (?1566–1626), courtier and religious controversialist. From un- + labouring.
英汉双解词典包含464360条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。