Abbreviations

TTC - Trying to conceive
BFP - Big Fat Positive (positive pregnancy test)
BFN - Big Fat Negative (negative pregnancy test)
CD - cycle day (day of cycle counting first day of flow as CD1)
OPK - Ovulation predictor kit
AMA - Advance Maternal Age (35+)
AF - Aunt Flo (menstrual flow)
2WW - Two week wait between ovulation and the time one is likely to discover if she is pregnant
DPO - days post ovulation

Here is a more comprehensive list of terms you might see flying around in online forums:
www.babycenter.com/community-help-abbreviations