Main Entry: me·si·al Pronunciation: 'mE-zE-&l, -sE- Variant: alsome·sal/-z&l, -s&l/ Function:adjective 1: being or located in the middle or a median part mesial aspect of the metacarpal head> 2: situated in or near ordirected toward the median plane of the body mesial to the lungs> —compare DISTAL 1b 3: of, relating to, or being the surface of a tooth that is next to the tooth in front of it or that is closest to the middle of the front of the jaw —compare DISTAL 1c PROXIMAL 1b —me·si·al·ly/-E/adverb