{i} person who substitutes or fills in to do the job of someone else of the same profession who is temporarily absent
someone (physician or clergyman) who substitutes temporarily for another member of the same profession
A locum is a doctor or priest who does the work for another doctor or priest who is ill or on holiday. a doctor or priest who does another doctor's or priest's work while they are on holiday, ill etc (locum tenens C17- 21), from , )