Nugatory, a.
Etymology: [L. nugatorius, fr. nugari to trifle, nugae jests, trifles.]
1. Trifling; vain; futile; insignificant.
2. Of no force; inoperative; ineffectual. If all are pardoned, and pardoned as a mere act of clemency, the very substance of government is made nugatory. I. Taylor.
Shades of meaning
Fernald has no entry of its own for nugatory; he lists it under vain.
He lists it without comment; the entries above explain its neighbors.