1) An infestation with lice 
• (n.) A disease (morbus pediculous) consisting in the excessive multiplication of lice on the human body.
(thir-i´ә-sis) pediculosis pubis.
An infestation with lice
Phthi·ri'a·sis noun [ Latin , from Greek ..., from ... louse.] (Medicine) A disease ( morbus pediculous ) consisting in the excessive multiplication of lice on the human body. 
phthiriasis, phtheiriasis; pediculosis Infestation with any type of human lice.