From Longman Dictionary of Contemporary Englishgeldgeld /ɡeld/ verb [transitive] HBATAto remove the testicles of a horse→ See Verb table
Examples from the Corpus
geld• In general, it is best to geld a colt before he is one-year old.• The 4-year-old gelding had never encountered a sloppy track before, but took to it immediately.• In the process, the people often gelded themselves.• Chester, a chestnut gelding with three white socks, was a particular family pet.Origin geld (1200-1300) Old Norse gelda 