In the shopping centre, I felt an almost irresistible temptation to buy things I didn't really need.

temptation 是名词，来自动词 tempt（诱惑、引诱），加上名词后缀 -ation 构成。temptation 指"诱惑、引诱"，表示让人产生强烈欲望去做某事的状态或事物。在这里指购物时产生的购买冲动。