Longman Dictionary of Contemporary English - weaken

~ v 1 »MAKE LESS POWERFUL« to make someone or something less powerful or less important, or to become less powerful  (Russia's influence on African affairs has weakened.) 2 »PHYSICALLY« T often passive) to make someone lose their physical strength, or to become physically weak  (Julia was weakened by her long illness.) 3 »BUILDING/OBJECT« to become less strong and less able to support a lot of weight  (The explosion severely weakened the foundations of the house.) 4 weaken sb's determination/resolve to make someone less determined  (The opposition she encountered did nothing to weaken her resolve.) 5 »BECOME LESS CERTAIN« to become less determined, especially so that you change your opinion and accept someone else's  (I think Mum's weakening about us going to that party.) 6 »MONEY« if a particular country's money or a company's share2 (5) prices weaken or are weakened, their value is reduced.