Is wearing tight, long trousers forbidden?

It is permissible for a man to wear trousers if they cover the 'awrah (private parts). It is disliked if they define it (revealing the 'awrah's outline due to thinness, tightness, or a belt), and even if this is outside of prayer, it compromises dignity. This dislike is qualified to situations where there is nothing else worn over them to prevent the 'awrah's outlines from being revealed.