for me a "transitional fossil" is a fossil that's part say fish and part frog.
How much fish and how much frog? Along that line of development we have such varying delights as Achoania, Osteolepis, Styloichthys, Eusthenopteron, Panderichthys, Crassigyrinus, Tiktaalik, Ichthyostega, Acanthostega, and Triadobachtratus. Take your pick.