na-adjective, noun
Describes a person or attitude that is overly idealistic, prone to daydreaming, or out of touch with reality. Often carries a mildly critical tone.
See also: 勝ち (がち)
彼は夢見がちな性格で、いつも非現実的な計画を立てている。
He has a dreamy personality and is always making unrealistic plans.
夢見がちなことを言う前に、現実を見なさい。
Before you say something fanciful, look at reality.
Compound of 夢見 (yumemi, 'dreaming') + suffix がち (-gachi, 'tending to'). The suffix がち attaches to nouns or verb stems to indicate a tendency or frequent occurrence, often with a negative nuance.