A malignant disease or growth is cancer or is related to cancer, and is likely to be harmful.

The process by which malignant cancer cells multiply isn't fully understood. 人们尚未完全了解恶性癌细胞的繁殖过程。

Is the tumour malignant or benign? 这个肿瘤是恶性的还是良性的？

Compare: benign (DISEASE)

having a strong wish to do harm

He developed a malignant hatred for the land of his birth. 他对自己的故土产生了强烈的怨恨。