Definition of "ex"

Thus first C checks to see if ex and wye are equal. The resulting value of 1 or 0 (true or false) then is compared to the value of zee.

1984 Waite, Prata & Martin, C (Computer Program Language), p. 190

When between the station and the junction I was looking to the rear of the train on the near side, thinking it possible that we might receive a signal from the guard to shunt at Swindon junction to allow the 2.27 a.m. fast train ex Derby to pass, but the guard did not give any signal

1885, F. A. Marindin, quoting Arthur Oakes, edited by Henry G. Calcraft, Annual Reports, Returns, Etc‎, Midland Railway - inquiry into the causes of a collision at Swinton station, page 96

The train was the 12.40 p.m. ex Derby on January 14th, 1914

1921, John Hope Fellows, editor, The Locomotive News and Railway Contractor, Volumes 8-10‎, Locomotive news agency, page 34

All trains from start of service up to the 13.57 ex Norwich (16.45 ex Nottingham) are 4 cars between Nottingham and Liverpool and all East bound trains are 4 cars from Liverpool Lime Street as far as Nottingham.

2003 February 11, "Fat Richard", “Re: Chiltern not stopping at Warwick Parkway”, in uk.railway‎ (Usenet), retrieved 11 June 2018, message-ID <2a1e76b8-185c-4b27-a8d2-6f3f3331f6cd@dp10g2000vbb.googlegroups.com>

The outward timing is: Ashford International railway station (domestic side) *departs at 09.25hrs* (connecting with the 07.32 ex Brighton *Marshlink* train and, 08.37 ex London St. Pancras International *HS1* train)

2016 March 17, Derek Jones, “South East Bus Festival, Detling, 2 April 2016”, in Invicta Newsgroup‎ (Usenet), retrieved 11 June 2018, message-ID <CAJ9GgXJNSabs=QsEzzf-tCXQcXPdZyRZgiEtk9J3e8ToRs+ctg@mail.gmail.com>