› [U] a situation in which someone or something is at a low level or is not strong or successful: weakness against sth The dollar's weakness against the Euro has made European goods more expensive here. weakness in sth Weakness in the economy is accelerating. She is concerned by the weakness of Europe's single currency. › [C] a particular part or quality of someone or something that is not good or effective: A smart management team knows its company's strengths and weaknesses. There are definite weaknesses in their security arrangements. His main weakness is his inability to delegate.