What is plural word for umbilical?

There is no singular or plural form for "umbilical." "Umbilical" is an adjective meaning "relating to the navel."

If you're looking for a plural word to describe multiple navels, you could use:

* navels

* umbilici (Latin plural)

For example, you could say "The doctor examined the patient's navels" or "The artist depicted multiple umbilici in their painting."