In the Hanoverian army at this time all officer ranks up to Oberst-Lieutenant could be held on a 'Titular' basis (they are noted as 'Tit.' in the 'Staats-Kalender'). I think that the nearest equivalent is brevet rank in the British army. In the 'Annalen der Braunschweig-Luneburgischen Churlande' the officers given acting or provisional rank when the Hanoverian corps taken into British pay was being mobilised, are described as 'mit dem Charakter von...'

It is translated as Brevet in Ducket's German-English-French Military Dictionary (p. 369) - see https://books.google.co.uk/books?id=HEkMAQAAMAAJ&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false