bug · noun C /bʌg/
bug (INSECT)
B1 a very small insect
Dictionary example:
He found a bug in his bed.
Learner example:
Maybe you're thinking that he's a loving man who talks only about bugs and insects, but it's not true. (Preliminary English Test; B1; Italian)
bug (ILLNESS)
B2 a bacteria or a virus causing an illness that is usually not serious
Dictionary examples:
I had a stomach bug last week.
There's a bug going around.
bug (COMPUTER)
B2 a mistake or problem in a computer program
Dictionary example:
A bug had caused the company's computer system to crash.
Learner example:
For instance, the millennium bug [might] make all computers confuse[d], and banks will lose money. (First Certificate in English; B2; Chinese)