I've been ttc for 9mo. and want to start doing cross fit. worried about "excessive" exercise affecting my fertility what is ment by excessive exercise?

Inexact term: You are right, "excessive" is not a medical term and is too vague to be helpful. I suggest anyway that crossfit is more intense than ideal for ttc. There are many healthy, fun exercise programs you can do while ttc; crossfit and 'boot camp' type programs may be a little much. Just an opinion.

Alter cycles: Too much exercise can definitely alter your menstrual cycle due to anovulation which leads to infertility. But it usually takes a lot. I don't know what your weight is but if you're doing it to keep a healthy weight then you should be fine and that is definitely encouraged. Search "female athletic triad" for excessive exercise effects on fertility.