OD - Overdraft
With "overdraft" facility in your current account, you may withdraw money more than your account balance. For example, you have given a cheque of Rs. 15 lakh to someone and you have only Rs. 12 lakh balance in your account. Now, if you have more than 3 lakh overdraft limit in your account, that cheque would be cleared with "3 lakh" overdrawn from your account.
It is kind of a small loan given for a short period of time. Some banks don't even charge any interest on the overdrawn money. For an overdraft facility you must have a good past record with the bank.
OD - Doctor of Optometry
Doctor of Optometry is the study of examining the sight, vision correction and management of vision changes. A doctor who practices Optometry is called an Optometrist. Unlike Ophthalmologist, an optometrist is not a medical doctor.
Optometrists are licensed to perform eye examinations, vision tests, prescribing correct lenses, detecting eye diseases and prescribing medicines for them.
OD - On Duty
"On Duty" is the term used to refer a situation where an employee is not available in the office , as he is "out" for some office work.
OD - Overdose
"Overdose" refers to the use of drug in quantity more than recommended by the physician.