Definition from Wiktionary, the free dictionary
- Rhymes: -aʊzi
- Remarkably bad; of poor quality, dirty, or underhanded; mean, contemptible.
- No offense, but your cooking is lousy.
- Infested with lice.
- (colloquial) Filled or packed with something.
- The place was lousy with students.
- She's lousy with credit cards, goes shopping every day!
Usage notes 
Prior to World War II, it was an offensive insult, implying filthiness. Now considered a mild or rather dated term.
remarkably bad; of poor quality, dirty, or underhanded
Infested with lice