noxious

/ˈnäk-shəs/

Middle English noxius, borrowed from Latin noxius "guilty, delinquent, harmful, injurious" (derivative of noxa "injurious behavior, harm, mischief") + -us -ousnoxa derivative (perhaps with -s- as a desiderative suffix) from the base of nocēre "to damage (things), injure, harm (persons)," going back to Indo-European *noḱ-éi̯e- "destroy" (with semantic weakening in Latin), whence also Sanskrit nāśáyati "(s/he) destroys," causative derivatives from a verbal base *neḱ- "disappear, pass out of existence, perish," whence, with varying ablaut grades, Sanskrit náśyati "(s/he) is lost, perishes," Avestan nąsat̰ "has gone away, is lost," Tocharian B näk- "destroy," (in middle voice) "disappear, be destroyed"

adjective

  1. physically harmful or destructive to living beings

  2. constituting a harmful influence on mind or behavior; especially : morally, corrupting

  3. disagreeable, obnoxious

noxious waste

pernicious baneful noxious deleterious detrimental mean exceedingly harmful. pernicious implies irreparable harm done through evil or insidious corrupting or undermining. baneful implies injury through poisoning or destroying.