skullcap

nouns

rounded brimless cap fitting the crown of the head
skullcap
is a type of (narrower)
a tight-fitting headdress
cap
a herbaceous plant of the genus Scutellaria which has a calyx that, when inverted, resembles a helmet with its visor raised
helmetflower, skullcap
the dome of the skull
calvaria, skullcap