na-adjective
Describes something that is not complete or total; often used with nouns or as an adverb with に.
その情報は部分的にしか正しくない。
That information is only partially correct.
彼は部分的な解決策
He proposed a partial solution.
完全 means 'complete' or 'perfect', the opposite of 部分的.
Compound of 部分 (ぶぶん, 'part') and the adjectival suffix 的 (てき, '-like, -al').