As nouns the difference between horse and capel
is that
horse is a hoofed mammal,
equus ferus caballus , often used throughout history for riding and draft work or
horse can be (uncountable|slang|dated) heroin while
capel is a horse or
capel can be (mining) a composite stone (quartz, schorl, and hornblende) in the walls of tin and copper lodes.
As a verb horse
is to frolic, to act mischieviously (usually followed by "around").