Green’s Dictionary of Slang

fornicating adj.

a lit. euph. for fucking adj.

1833		Satirist (London) 12 May 3/3: ‘Treat you to a Sue, you fornicating enormity?’ shrieked the affrighted gentleman ‘no, not if Sues and Dollies were as plentiful as paving stones!’ .
1936		in Dos Passos Fourteenth Chronicle (1973) 483: This novel business is an awful business. Why the hell did I ever get mixed up in it? [...] And even at that the fornicating business wont get itself finished.
1971		(con. WWII) B. Aldiss Soldier Erect 106: Not in my bloody fornicating life.
1973		B.S. Johnson All Bull 34: Ask some of these fornicating friggers who live in this one-horse town!

SE in slang uses

In compounds

fornicating engine (n.) (also fornicating member, ...tool) [engine n./member n.¹ /tool n.¹ (1a)]

the penis.

1890–1904

Farmer & Henley Sl. and Its Analogues III 60/1: Fornicating-engine (-member; -tool) [...] (venery) The penis.