There are various high level spells named “Power Word: X”. They are all verbal-only spells (except Power Word: Heal), and tend to have the following text in them(…except Power Word: Heal):
You speak a word of power that [has the effect of the spell’s name]
Assume for the purpose of the question that the rules from Xanathar’s Guide on spell identification are in use.
Do these properties (verbal only, verbal component is a single word rather than multiple) make these spells unusually easy to identify – not as a specific spell, but as “one of the Power Word spells”?
In other words, consider the following scenario:
Spellcaster A is facing off against spellcaster B. On B’s turn, B utters a single arcane word, and seems to not be using any somatic or material components for their spell.
Is it reasonable for A to deduce, without the use of a reaction, “ah, I reckon the single word and nothing else means it’s one of the Power Word spells. I had better Counterspell using a high level slot”?