To fondle or caress means to touch, handle or stroke tenderly, affectionately, or erotically. The passive form is to be fondled or to be caressed. Fondling and caressing is both the present participle of fondle/caress, and a noun referring to such an activity. In addition, fondling is also a noun referring to a pet or person who is fondled.
Sexual fondling, especially in a paraphilic nonconsensual form such as to strange persons on a crowded train, is also known as frotteurism. When sexual fondling is unwelcome and unconsensual, it is also called groping and may be considered sexual assault.