1. Of, relating to, directed toward, or situated at the front: a frontal attack. (wiktionary.org)
2. Of or relating to the forehead or frontal bone. (wiktionary.org)
3. Of or relating to the frontal plane. (wiktionary.org)
4. Belonging to the front part. (wordnetweb.princeton.edu)
5. Of or adjacent to the forehead or frontal bone. (wordnetweb.princeton.edu)
Word origin: From Modern Latin frontalis, from front-, stem of frons “brow, forehead”. Or in some cases probably from front (n.) + adjectival suffix –al.