Terminal velocity is the maximum velocity reached by an object falling in a fluid (for example, the maximum velocity you attain when falling out of a plane). The drag force, which depends on the velocity, prevents continued acceleration; acceleration tends to zero in the presence of drag, so velocity tends to a constant value.
``Laminar velocity'' isn't really a specific term, but laminar flow refers to smooth flow of a liquid. In contrast, turbulent flow happens when there are jiggles and eddies. The drag force is different in the laminar and turbulent cases, and hence the terminal velocity is different according to whether the flow of the fluid around the object is laminar or turbulent.