For the adjective meaning deficient or lean, meager is the preferred spelling in American English. Meagre is preferred in all other varieties of English. Other than the spelling, there is no difference between the two forms.
Outside the U.S.
So how did a battle over a $3.6-trillion (U.S.) budget boil down to a fight over a meagre $75-million in funding for Planned Parenthood? [Globe and Mail]
Three championship victories all season reflected meagre bowling stocks and injuries to key players. [Guardian]
Six rounds gone and the Broncos have conceded a meagre 50 points. [The Australian]
If your writeoffs are comparatively meager, you might be inspired to look harder for ones you’ve missed. [Forbes]
For 120 minutes I waited for any meager throwaway gesture from Aiken to show me what kind of man he is … [The Atlantic]
That’s because when well-drained, nutrient-meager soils combine with cool temps, cabernet matures longer on the vine. [Chicago Tribune]