afterthought

1. N-COUNT If you do or say something as an afterthought, you do or say it after something else as an addition, perhaps without careful thought. 事後的想法; 馬後砲[usu sing, usu 'a' N]

Almost as an afterthought he added that he missed her. 幾乎是後來想起來，他補了句他想她了。