When something is sinking in, it means that it is slowly beginning to be understood or realized. There are many synonyms we can use to describe this feeling. One such word is comprehending, which means understanding something fully. Another synonym is grasping, which means to hold onto or understand something firmly. The word apprehending can also be used to describe the process of slowly beginning to understand something. Similarly, the word realizing can be used to describe the gradual process of recognizing or becoming aware of something. In essence, all of these synonyms capture the feeling of slowly but surely understanding something that was previously unclear or confusing.