constrained

(verb) hold back. Synonyms: restrain, encumber, cumber, constrain.

(verb) restrict. Synonyms: stiffen, tighten, tighten up, constrain. Examples: "Tighten the rules." "Stiffen the regulations."

(adj) lacking spontaneity; not natural. Synonyms: forced, strained. Examples: "A constrained smile." "Forced heartiness." "A strained smile."