"Getting up in years" is an idiomatic phrase that refers to becoming older. It is often used to describe someone who is approaching or has already reached their senior years. There are several synonyms for this phrase that can be used interchangeably. One such synonym is "aging," which suggests the gradual process of getting older. Another synonym is "growing older," which highlights the ongoing nature of the aging process. "Maturing" is another word that can be used to convey a more positive connotation of aging, suggesting personal growth and development. Finally, "advanced in age" is a formal synonym used to describe someone who is older and may require more assistance with daily tasks or routines.