sharp enough to cut glass

1. Having a very prominently defined point or edge. Often said of physical features. It used to be the case that you had to have cheekbones sharp enough to cut glass if you wanted to be a model, but those standards are starting to change. The movie star has such strong features, with piercing blue eyes, an impressive physique, and a jawline that looks sharp enough to cut glass.

2. Harsh, bitter, or hurtful, as of one's voice, words, or tone. I knew Mom was furious as soon as she opened her mouth, her tone sharp enough to cut glass. I hate working with that guy. His so-called "constructive criticism" is always sharp enough to cut glass.