The definition of "first time homebuyer" depends on where you are using it.
If you are referring to the exception to the penalty levied on an early distribution from an IRA to buy a home, then the definition for homebuyer in this case follows.
The IRS says,
"
First-time homebuyer.
Generally, you are a first-time homebuyer if you had no present interest in a main home during the 2-year period ending on the date of acquisition of the home which the distribution is being used to buy, build, or rebuild. If you are married, your spouse also must meet this no-ownership requirement.
" See IRS Pub 590.