ump

noun

A person, usually appointed, who decides the issues or results, or supervises the conduct, of a competition or conflict: arbiter, arbitrator, judge, referee, umpire. Sports ref. See decide/hesitate.

Uridine 5′-monophosphate, a pyrimidine nucleotide.

• UMP synthase deficiency — an inherited absence of the enzyme, which assists in the conversion of orotate to UMP, results in the accumulation of orotate and its excretion in large amounts in the milk. Bovine homozygotes for the condition die at fetal age of about 40 days.

The noun has one meaning:

Meaning #1: an official at a baseball game
  Synonym: umpire