adverb.
In an accidental manner; unexpectedly; by chance; casually; fortuitously.
adverb.Unintentionally.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adverb.
without intention; in an unintentional manner
adverb.
of a minor or subordinate nature
adverb.
without advance planning
Word Usage
"The sitting-room has its solitary moments, when any two boarders who wish to meet may come together accidentally, (_accidentally_, I said, Madam, and"