There are various synonyms for the term "grand-dad." Some of them are grandfather, grandpa, gramps, pop, papa, and old man. These terms evoke a sense of warmth, familiarity, and respect. "Grandfather" is a more formal term, while "gramps" or "pop" are more endearing terms used to signify a closer relationship. "Papa" is a term often used by grandchildren to signify a strong bond with their grandfather. "Old man" is a term that can be used affectionately between family members but may be considered impolite when used by strangers. Regardless of the term used, grandfathers are an important figure in many people's lives.