impermissible

/ɪmˈpʌrˌmɪsəbəl/

Something impermissible isn't allowed. It's impermissible in every part of the U.S. to drive 100 miles an hour on the highway.

Things that are permissible are legal, authorized, or welcome — you are permitted to do them. The opposite of permissible is impermissible, which adds the "opposite" prefix im- to permissible, from the Latin permittere, "let, allow, grant, or permit." It's impermissible to bully other kids at school, or against the rules, and it's impermissible to steal a car, or against the law.

Definitions of impermissible

1. adjective

   not permitted
   “impermissible behavior”

   synonyms:

   forbidden, out, prohibited, proscribed, taboo, tabu, verboten

   excluded from use or mention

   unmentionable

   unsuitable or forbidden as a topic of conversation

   untouchable

   forbidden to the touch

   intolerable, unbearable, unendurable

   incapable of being put up with

   antonyms:

   permissible

   that may be permitted especially as according to rule

   tolerable

   capable of being borne or endured
2. adjective

   not allowable
   synonyms:

   inadmissible

   not deserving to be admitted