While driving, I listened to some old shiurim from Aish Audio. They're of varying quality, both in substance and recording. One interesting lecture talked a lot about nebbochs. I'd forgotten how much I enjoy the Yiddish words nebbish and nebboch (aka nebech). My friend Ilan taught me the word nebbish over Shabbos several months ago. He had a great way of defining it, but I don't think it works as well in writing. However, Southern speech has a great way of conveying the idea: "Bless his heart, he just tries so hard." Southerners are masters of "concerned criticism." If you are a visual learner, I suggest taking a walk down memory lane with Screech (Saved By the Bell) and Steve Urkell (Family Matters).
Nebbish seems to be both an adjective and a noun, but nebboch seems to only be a noun.
Dictionary.com defines them as "A person, esp. a man, who is pitifully ineffectual, timid, or submissive." My favorite definition I discovered online was "a sad sack." If you're unimaginative, a nebboch is a perpetual loser.