Adjectival phrases are phrases that function as adjectives. They consist of the adjective(s) that modifies a noun and any adverb(s) or other elements that modify that adjective.
Adjectival phrases always occur inside noun phrases.
They always have a house full of friends during the summer.
She prepared a wonderfully light meal.
Adjectival phrases can also complete the verb, acting as complement.
She is really boring.
Today the weather was sunny and hot, so we decide to go to the beach.
Noun Phrases in English Grammar – how to identify them and use them.