I'm biased, but I think you have plenty to gain from SS. Muscle definition is a function of muscle size plus reduced body fat, but getting stronger is always important. SS is a novice barbell program (which is what you are), designed to build up a good base of strength. That strength will make future goals that much easier to achieve - even bodybuilders start with this, because a good strength base means you'll use heavier and therefore more effective weights on a hypertrophy program.
But your muscles will grow, especially if you eat enough. And you will PR at every workout, because that's what linear progression is. Give it a year, follow the program, and re-assess from there. Also, check out the Starting Strength forum, because lots of really great coaches (even Rip himself) hang out there and give advice and address technique.