The term 'HALT! TO A STALLION' is a command used to stop a horse. The crossword solutions for this term are 'WHOA', which is an interjection used to express surprise, disbelief, or to get someone's attention. It is also used as a command to stop a horse, and is derived from the Middle English phrase 'hwaet'. This phrase was used to call out to horses in order to stop them, and has since been shortened to 'WHOA'.