'Hay knife' definitions:

Definition of 'Hay knife'

From: GCIDE

Hay \Hay\, n. [OE. hei, AS. h[=e]g; akin to D. hooi, OHG. hewi, houwi, G. heu, Dan. & Sw. h["o], Icel. hey, ha, Goth. hawi grass, fr. the root of E. hew. See Hew to cut.] Grass cut and cured for fodder. [1913 Webster]
Make hay while the sun shines. --Camden. [1913 Webster]
Hay may be dried too much as well as too little. --C. L. Flint. [1913 Webster]
Hay cap, a canvas covering for a haycock.
Hay fever (Med.), nasal catarrh accompanied with fever, and sometimes with paroxysms of dyspn[oe]a, to which some persons are subject in the spring and summer seasons. It has been attributed to the effluvium from hay, and to the pollen of certain plants. It is also called hay asthma, hay cold, rose cold, and rose fever.
Hay knife, a sharp instrument used in cutting hay out of a stack or mow.
Hay press, a press for baling loose hay.
Hay tea, the juice of hay extracted by boiling, used as food for cattle, etc.
Hay tedder, a machine for spreading and turning new-mown hay. See Tedder. [1913 Webster]