Green’s Dictionary of Slang

1. the heart.

1909		J. Ware Passing Eng. of the Victorian Era.
2017		http://www.cockneyrhymingslang.co.uk 🌐 Horse and Cart is Cockney slang for Heart.

2. (Aus.) the start.

1905		Duke Tritton’s Letter n.p.: I think I had better tell you the Grim and Gory right from the Horse and Cart.
2002		Pete’s Aussie Sl. Home Page 🌐 horse and cart: the start.

3. a tart.

1972

Dodson & Saczek Dict. of Cockney Rhy. Sl.

4. a breaking of wind [= fart n. (1)].

1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Horse and cart. Flatulence. Rhyming slang for fart.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 90/2: horse and cart n. a fart.
2003		B. Dark Dirty Cockney Rhy. Sl.