“意志薄弱的”可以用英语表达为 "weak-willed" 或 "lacking in willpower"。
"weak-willed" 是形容词短语,直接描述某人意志不坚定,容易受外界影响或放弃目标。例如:He is a weak-willed person who often gives in to temptation.(他是一个意志薄弱的人,经常屈服于诱惑。)
"lacking in willpower" 是动词短语,强调缺乏坚持或抵抗的能力。例如:She tends to give up easily because she is lacking in willpower.(她容易放弃,因为她缺乏意志力。)
根据语境选择合适的表达即可。