If you aren't happy with your definition retention, why not start marking definitions as '2' rather than '3' if your recall of them is slower than you might like?

How are the mnemonics you use? It sounds strange to say you're disappointed with your level of retention when your settings are at 95%. Perhaps that's somewhere you could improve.

Definition retention rates are usually lower, because 1) the flashcard action is not as good as active recall, 2) the answers aren't as clear-cut as for the other prompt types, and 3) you don't review character-level definitions in the course of doing word-level definition reviews.

When you say that you're disappointed by the definition retention rate, do you notice yourself being disappointed in how often you forget definitions, or is it just that the Skritter-reported retention rate number is lower than you would like?