1) Upper-lip groove 
The philtrum (philtrum, φίλτρον philtron) is a vertical groove in the middle area of the upper lip, common to many mammals, extending from the nose to the upper lip. Technically referred to as the medial cleft, together with a glandular rhinarium and slit-like nostrils, it is believed to constitute the primitive condition for mammals in gen...
The area from below the nose to the upper lip. Normally the philtrum is grooved. In foetal alcohol syndrome, the philtrum is flat. ... (12 Dec 1998) ... 
(fil´trәm) the vertical groove in the median portion of the upper lip.
The hollow in the face above the centre of the upper lip
Type: Term Pronunciation: fil′trŭm, -tră Definitions: 1. A philter or love potion. 2. The infranasal depression; the groove in the midline of the upper lip.
Philtrum: The area from below the nose to the upper lip. Normally the philtrum is grooved. In fetal alcohol syndrome, the philtrum is flat.
Greek philtron - the median sulcus of the upper lip. Derivation doubtful.