unadvertised en · ADJ
Etymology
From Middle English unadvertised, equivalent to un- + advertised.
Meanings
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(not-comparable) Not advertised
Once the party outing season in June is over, Saturday long-distance traffic at Waterloo closely follows the public timetable and few unadvertised relief trains have to be run.
1962 April, J. N. Faulkner, “Summer Saturday at Waterloo”, in Modern Railways, page 263: