Definition of keel:

part of speech: verb

To navigate; to turn keel upwards.

part of speech: noun

The principal and lowest timber in a ship, extending from stem to stern, and supporting the whole frame; a low flat- bottomed vessel; in bot., a projecting ridge, rising along the middle of a flat or curved surface; the two lowermost, and more or less combined, petals of a papilionaceous corolla.