o·ver·act 
(ō′vər-ăkt)
(ō′vər-ăkt)v. o·ver·act·ed, o·ver·act·ing, o·ver·acts
v.tr.
To act (a dramatic role) with unnecessary exaggeration.
v.intr.
1. To exaggerate a role; overplay.
2. To act over and above what is required; overdo in acting.
o′ver·action n.