An adjective phrase or adjectival phrase is a phrase that describes and modifies the noun. It could be used as attributive or predicative. Attributive adjective is included in the in the noun phrase it modifies while predicative adjective is not included in the noun phrase it modifies. In the sentence, Snow throughout April was quite a surprise this year; the adjective phrase is quite a surprise. ‘Quite’ is the adjective describing he noun ‘surprise’.