Is staring at someone on the job considered sexual harassment?

Sexual harassment is completely context or fact dependent--that means, it depends on the circumstances. Looking at a woman once--almost certainly not. Staring at a woman on the day she forgot to wash off face paint from her child's birthday party--again, likely not, since there's a good reaons or excuse. Staring at a female coworker extensively and intently, or on repeated occasions when there isn't a good reaons for it--very possibly sexual harassment.

So staring could be sexual harassment--it depends on how, when, whom, how, etc.; i.e. it depends on the facts.