ζέωzéō

to boil, be hot; metaphorically, of anger, love, zeal: participle, fervent: τ.

Greek (New Testament) · G2204

Meanings

πνεύματι, Acts 18:25, Romans 12:11.

Same root

ζῆλοςzēlos · G2205properly, heat, i.e. (figuratively) "zeal" (in a favorable sense, ardor; in an unfavorable one, jealousy, as of a husband (figuratively, of God), or an enemy, malice)
ζύμηzýmē · G2219ferment (as if boiling up)
ζεστόςzestós · G2200boiled, i.e. (by implication) calid (figuratively, fervent)

Where it appears

Appears 2 times in the Bible.

Acts 18:25 He had been taught the way of the Lord, and he taught others about Jesus with an enthusiastic spirit and with accuracy. However, he knew only about John’s baptism.
Romans 12:11 Never be lazy, but work hard and serve the Lord enthusiastically.

Source: G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922), public domain.