to allow (someone) to be by himself or herself: Leave him alone—he wants to rest.
b.
to refrain from annoying or interfering with: The youngsters wouldn't leave the dog alone, and he finally turned on them.
8.
let alone,
a.
to refrain from annoying or interfering with.
b.
not to mention: He was too tired to walk, let alone run.
9.
let well enough alone, to be satisfied with the existing situation; refrain from attempting to change conditions: Marriages are often destroyed by relatives who will not let well enough alone.
Origin: 1250–1300;Middle Englishal oneall (wholly) one
Related forms
a·lone·ness, noun
Synonyms 1. single, solitary; unaccompanied, unattended. Alone, lone, lonely, lonesome all imply being without companionship or association. Alone is colorless unless reinforced by all; it then suggests solitariness or desolation: alone in the house; all alone on an island.Lone is somewhat poetic or is intended humorously: a lone sentinel.Lonely implies a sad or disquieting feeling of isolation. Lonesome connotes emotion, a longing for companionship.
c.1300 contraction of O.E. all ana "all by oneself," from all "all, wholly" + an "one" (see one). Similar compounds found in Ger. (allein) and Du. (alleen).