level-headed(s = adj.all) healthy, intelligent, levelheaded, sound - exercising or showing good judgment; "healthy scepticism"; "a healthy fear of rattlesnakes"; "the healthy attitude of French laws"; "healthy relations between labor and management"; "an intelligent solution"; "a sound approach to the problem"; "sound advice"; "no sound explanation for his decision"

level-headed, adj. mentally well-balanced, cool, sensible.

Derivative:
level-headedly adv. level-headedness n.