on calladv.adj.
/ˌɒn ˈkɔːl/, U.S. /ˈɔnˈkɔl/, /ˈɑnˈkɑl/ (in sense B.)Brit. /ˈɒnˌkɔːl/, U.S. /ˈɔnˈkɔl/, /ˈɑnˈkɑl/ A. adv.
Available; on standby, awaiting orders; ready to answer a call or summons immediately; spec. available to provide a professional service if and when required, esp. outside normal working hours.
ΚΠ
1858 G. H. Miles Senor Valiente iv. i. 33 Not so very busy?—only seven cases on call.
1897 B. Stoker Dracula xix. 255 That old place may be full of rats, and if so, I've got an antidote on call.
1915 C. P. Gilman Herland in Forerunner Mar. 70/2 From morning to night there was Somel, always on call except between two and four.
1938 Amer. Speech 13 228/2 Nurses take their turn being on call for emergency operations.
1977 ‘J. le Carré’ Honourable Schoolboy i. iv. 76 Sam should lie up in the rumpus room to be on call.
2001 C. Glazebrook Madolescents xii. 113 And the answering machine. Not much use since they cut the phone off though... It's an extension off the café phone now. I'm on call, like a doctor, in case there's an emergency.
B. adj.
Usually hyphenated. Immediately available; on duty; spec. of, relating to, or participating in a professional service whereby a designated person or team is available to provide a service if and when required, esp. outside normal working hours.
ΚΠ
1946 Amer. Jrnl. Sociol. 52 170/2 The medical profession, frequently represented only by an ‘on-call’ physician.
1967 Nursing Times 27 Jan. p. xlix/1 (advt.) Two Staff Nurses... No on-call duty.
1994 Richmond (Va.) Times-Dispatch 24 Dec. b3/1 The on-call detective works from 9 a.m. to 5 p.m.
This is a new entry (OED Third Edition, June 2004; most recently modified version published online March 2022).
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adv.adj.1858