to puzzle, perplex, baffle, bewilder (somebody); to afflict by being complicated, contradictory, or otherwise difficult to understand
To mix up, muddle up (one thing with another); to mistake (one thing for another).
To mix thoroughly; to confound; to disorder.
To be confused.
To believe, to think one grasps sufficiently despite potentially incomplete knowledge.
To stand underneath, to support.
To grasp a concept fully in one's mind, especially (of words, statements, art, etc.) to be aware of the meaning of and (of people) to be aware of the intent of.