Entry 1 sense Webster, 1913 Indefatigability /(ĭn`dē̇*făt`ĭ*gȧ*bĭl"ĭ*ty̆)/ · In·de·fat·i·ga·bil·i·ty · IPA 01 n. The state of being indefatigable. 1. The state of being indefatigable.