Dispassionate, a.
1. Free from passion; not warped, prejudiced, swerved, or carried away by passion or feeling; judicial; calm; composed. Wise and dispassionate men. Clarendon.
2. Not dictated by passion; not proceeding from temper or bias; impartial; as, dispassionate proceedings; a dispassionate view.
Syn. -- Calm; cool; composed serene; unimpassioned; temperate; moderate; impartial; unruffled. -- Dis*pas"sion*ate*ly, adv. -- Dis*pas"sion*ate*ness, n.
Shades of meaning
Fernald has no entry of its own for dispassionate; he lists it under calm.
He lists it without comment; the entries above explain its neighbors.