The Collaborative International Dictionary
Umbilication
Umbilication \Um*bil"i*ca"tion\, n. A slight, navel-like depression, or dimpling, of the center of a rounded body; as, the umbilication of a smallpox vesicle; also, the condition of being umbilicated.
Wiktionary
umbilication
n. A slight, navel-like depression, or dimpling, of the centre of a rounded body.