inobservant

in·ob·ser·vance

 (ĭn′əb-zûr′vəns)
n.
1. Lack of heed or attention; disregard.
2. Nonobservance, as of a law or custom.

in′ob·ser′vant adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
References in periodicals archive ?
We have trained them to worry about it, and it is one of the few aspects of bird health that can be tracked by an inobservant owner.
An inobservant American driver in New Zealand quickly discovers that his standard theories of driving are wrong when, driving on the right-hand side of the road in Auckland, he unavoidably enters into a head-on collision.