unmeant, undevised, odd, fluky, contingent, unintended, unwitting, accidental, unintentional, unplanned, unpremeditated, chance, casual, planned, unthinking, fortuitous, surprise, undesigned.
inattentive (part of speech: adjective)
neglectful (part of speech: adjective)
Like a spectre does that solemn, impalpable, often perfectly unreasonable omniscient and omnipotent entity lurk in the shadow ready to reach out a clutching hand, and for some infraction of regulations, wilful or inadvertent,
hale the luckless and shivering defaulter to judgment.
- "The Sky Pilot in No Man's Land", Ralph Connor.
If you stand near the nest of a bird that has young, she will not be induced to betray them by an inadvertent
fondness, but will wait about at a distance with meat in her mouth for an hour together.
- "The-Natural-History-of-Selborne", White, Gilbert.
All of these people I watched closely, half hoping that some inadvertent
sign might tell me of someone's knowledge of the secret.
- "The Gold Bag", Carolyn Wells.