beyond the pale

1. Totally unacceptable: “His business practices have always been questionable, but this last takeover was beyond the pale.” The Pale in Ireland was a territorial limit beyond which English rule did not extend.

Idioms and Phrases

Outside the bounds of morality, good behavior or judgment; unacceptable. For example, She thought taking the boys to a topless show was beyond the pale. The noun pale, from the Latin palum, meant “a stake for fences” or “a fence made from such stakes.” By extension it came to be used for an area confined by a fence and for any boundary, limit, or restriction, both of these meanings dating from the late 1300s. The pale referred to in the idiom is usually taken to mean the English Pale, the part of Ireland under English rule, and therefore, as perceived by its rulers, within the bounds of civilization.

Related Words

• banned www.thesaurus.com
• outlawed www.thesaurus.com
• prohibited 
• tabu www.thesaurus.com
• unthinkable