I was busy + (verb-ing)

When using the word 'was', you are referring to something in a past tense, or something that happened before.  Combining it with the word 'busy' you can express something that was occupying you in a past time.

Here are some examples:

"I was busy thinking."

"I was busy working."

"I was busy cooking dinner."

"I was busy talking on the phone."

"I was busy cleaning the house."

"I was busy studying for my test."

"I was busy thinking of ideas for our website."

"I was busy entertaining our neighbors."

"I was busy completing my housework."

"I was busy learning new things.