Verbs we commonly define as "action words." They indicate that some person or thing—the subject of the sentence—is performing some sort of action, or, conversely, that some sort of action is being performed on the subject. Take, for example, the following quotation:
Crowing respirations herald a pediatric emergency; stridor signals the gerontologist to begin a diagnostic evaluation.
Here the verbs, herald and signals, indicate what the respirations and the stridor are doing, and indicate it with vigor and precision. There is no doubt that these verbs represent action words.
Many verbs, as commonly used, have lost precision, and to convey finer shades of meaning they require some modification. We may, for example, say, "The man walked in the woods." This is a declarative sentence which, to be sure, conveys factual information but only a minimal degree of precise detail. To make the sentence more precise, to convey a more definite
King LS. Verbs. JAMA. 1967;202(1):45-46. doi:10.1001/jama.1967.03130140103018