The phrase "racing horses" refers to the activity or sport of horses running in a competition against each other to see who is the fastest. Full definition
In his early analysis, for example, the model said that the number of races a horse had previously run was a crucial factor when making predictions. (discovermagazine.com)
It's breeding for desired characteristics, like race horses and tiny fluffy dogs. (religion.blogs.cnn.com)
Mediation between owners of famous race horse concerning tax issues and returns on investment. (toddweld.com)