Definition of tweenie:
(n) :
(informal) A child who is not quite old enough to be a teenager; a tweenager.
(n) :
(tennis) A shot that is hit between the legs; a tweener.
(n) :
(slang) A 650-watt fresnel motion picture lighting instrument first manufactured by the Mole-Richardson Company.
(n) :
Alternative spelling of 'tweenie, tweeny or 'tweeny.