"Incomplete understanding" means that someone does not fully comprehend or know everything about a particular subject or concept. They may have some knowledge on the topic, but there are still gaps or things they do not know. Full definition
There is gift, beauty, understanding, and pleasure, but also mystery and not - knowing; we live with incomplete understanding of ourselves, our intimate partners, and the sacred. (rachelheldevans.com)
I was, however, pointing out that your comment is evidence that you have a very incomplete understanding of reason. (religion.blogs.cnn.com)
This is due, in part, to the medical community's incomplete understanding of how ADHD affects and manifests in girls, specifically. (additudemag.com)