When it comes to military terminology, "weapons free" is a phrase that refers to permission given to soldiers to use any available weapons without waiting for authorization. In terms of synonyms, "engaging targets" could be used to imply the same action, while "fire at will" is a more casual and colloquial way of saying the same thing. "Free to engage" is another alternative to "weapons free" that clearly indicates permission to fire on targets. Finally, "open fire" is a phrase that is often used to convey a sense of urgency in combat scenarios and could be another way of expressing "weapons free".