brute - Greek, “irrational.” In contrast to angels that “excel in strength.”
beasts - Greek, “animals” (compare Psa 49:20).
natural - transposed in the oldest manuscripts, “born natural,” that is, born naturally so: being in their very nature (that is, naturally) as such (irrational animals), born to be taken and destroyed (Greek, “unto capture and destruction,” or corruption, see on Gal 6:8; compare end of this verse, “shall perish,” literally, “shall be corrupted,” in their own corruption. Jud 1:10, naturally ... corrupt themselves,” and so destroy themselves; for one and the same Greek word expresses corruption, the seed, and destruction, the developed fruit).
speak evil of - Greek, “in the case of things which they understand not.” Compare the same presumption, the parent of subsequent Gnostic error, producing an opposite, though kindred, error, the worshipping of good angels”: Col 2:18, “intruding into those things which he hath not seen.”