1) Affected 2) Forced 3) Lacking spontaneity 4) Not natural 5) Stiff or unnatural 6) Strained 7) Unnatural 1) Bound 2) Compelled 3) Held in 4) Limited 5) Restricted 6) Uneasy 
• (a.) Marked by constraint; not free; not voluntary; embarrassed; as, a constrained manner; a constrained tone. • (imp. & p. p.) of Constrain
Con·strained' adjective Marked by constraint; not free; not voluntary; embarrassed; as, a constrained manner; a constrained tone. 
[adj] - lacking spontaneity
forced adjective lacking spontaneity; not natural; `a constrained smile`; `forced heartiness`; `a strained smile`
forced, compelled, or obliged: a constrained confession. · stiff or unnatural; uneasy or embarrassed: a constrained manner.
[Intelligent words] lacking spontaneity; not natural