1. The vertical and shallow groove going down the external and middle surface of the face below the nose and above the upper lip: The primary meaning of philtrum is said to be "love potion" which indicates that this facial feature has seductive or attractive and alluring powers.
2. Etymology: from ancient Greek philtron then from Latin philtrum, "love charm"; literally, "a means to make oneself beloved"; phileo, "to love, to kiss".