Definition
A combined navigation receiver mode, or a selectable function on a navigation indicator such as the HSI, that processes signals from either a VOR (VHF Omnidirectional Range) station or a localizer transmitter associated with an ILS approach. Both signals share the same VHF frequency band (108.00–117.95 MHz), so a single receiver can tune and display either type of guidance, and the indicator automatically interprets the signal appropriately for course deviation display.
Plain English
One radio and one needle that can show you either an airway course from a VOR station or the runway centerline from a localizer, depending on which frequency you tune in.
Context Anchor
Seen on a Horizontal Situation Indicator or navigation display when choosing what kind of radio navigation signal the instrument will show.
Derivation
VOR stands for VHF Omnidirectional Range — a station that broadcasts course information in every direction. Localizer is from Latin 'locus' (place), meaning the signal that locates you on the runway centerline. The slash combines them because the same receiver and the same indicator handle both.
Why Pilots Care
It lets the pilot follow a precise ground track using one instrument instead of switching between separate VOR and localizer displays.
Intuition Check
VOR/LOC does not mean the instrument is using VOR and localizer at the same time. It means the same display mode can show either VOR guidance or localizer guidance, depending on what signal is selected.
Example Sentence 1
After tuning the ILS frequency, the HSI's VOR/LOC needle became more sensitive as we intercepted the localizer.
Example Sentence 2
With the HSI in VOR/LOC mode the needle stayed centered all the way down the final approach course.