very thin, as thin as a hair
A fishing line made from hair.
The line along one's forehead where hair starts growing.
A very thin line in writing, drawing, or typography.
A very thin fissure.
Small (especially contemptibly small) in amount.
Particularly of pigs or pork: infected with larval tapeworms or trichinae (parasitic roundworms).
Of a person: infected with measles.