tiffany knew it was gibbous because she 'd read in the almanack that gibbous meant what the moon looked like when it was just a bit fatter than half full , and so she made a point of paying attention to it around those times just so that she could say to herself : `` ah , i see the moon 's very gibbous tonight ... . '' it 's possible that this tells you more about tiffany than she would want you to know .