The word "skindeep" refers to something that is only surface-level or superficial. Antonyms for this word would include phrases such as "deep-seated," "profound," or "meaningful." These words suggest a sense of significance and depth that is lacking in something that is only skin-deep. Other antonyms could include "genuine," "authentic," or "sincere," which connote a sense of honesty and truthfulness. Thus, we would use these antonyms to describe emotions, relationships, and experiences that are more than just fleeting or superficial; they are deeply felt, meaningful, and true to oneself.