A sense was one's ability to perceive the world through various means of input. The five most common senses were taste, touch, hearing, smell, and sight. Sensation was the process of using a sense to gather information and respond to a stimulus. Something could be described as sensual if it gratified the senses and gave physical pleasure.
According to Captain Jonathan Archer, Starfleet sent out Enterprise NX-01 to explore with their own senses instead of sending probes to take maps and pictures. (ENT: "Civilization")
In 2370, Doctor Beverly Crusher described what she thought to be the most physical dream she ever had, as the sensations were very real and extremely arousing. (TNG: "Sub Rosa")
In 2380, Jack Ransom stated "there's no peninsula more sensual than the Iberian." (LD: "Moist Vessel")