superficial knowledge; half-baked understanding
Describes knowledge or understanding that is shallow, incomplete, or not properly digested. Often used critically of someone who has only a surface-level grasp of a subject.
His explanation is superficial and lacks deep understanding.
Arguing with half-baked knowledge isn't persuasive.
Compound of 生 (nama, 'raw, unprocessed') and 飲み込み (nomikomi, 'swallowing, understanding'). The image is of swallowing something raw without properly digesting it, hence 'superficial understanding'.