One definition of hostile, according to Dictionary.com, is "not friendly, warm or generous." So, if your boss and co-workers are jerks, it may seem appropriate to say you have what is called a "hostile work environment."
However, be careful about using that phrase, especially if you decide to elevate an issue to human resources or management.
"Hostile work environment" in many instances is a legal term meaning that someone(s) in your workplace is acting illegally. That is, there is illegal discrimination based in the areas of gender, religion, race, pregnancy or disability, to name a few. If your complaint does not fall under one of these protected areas, then you may technically not have a hostile work environment. Claiming one when you are trying to make a stand against bullying can hurt your case and credibility.
It can be shocking and disheartening to realize that someone who has been taunting you for, say, always staying late and for being the boss's "pet" may not be acting illegally and may not be creating a hostile work environment in the way that the law recognizes. Does that mean there is nothing you can do? Of course not. You can always document the incidents and what exactly your tormenter has said. Upon further reflection, it might become clear that there is actually more going on. Perhaps that co-worker's choice of particular words does indeed show that you could have a "hostile work environment" claim.
Lacking that, though, your best bet might be to keep documentation and try to resolve the matter first with your co-worker and then with your supervisor. Similarly, if you have a boss who is inconsistent in that he or she keeps changing deadlines and expectations for important projects and generally just likes to complain about a lot--commutes, the decline of food quality, late workers--your best bet could be to try to address it head-on as a group with your colleagues. There might be nothing illegal about your boss's conduct although it is disheartening.