If the thought of the Temple of Elemental Evil is more appealing than going home to your wife, you might be an adventurer.
I went out for milk, and came back 15 years later. How was I supposed to know some wackos had moved in next door and sequestered my wife to worship!
You may be an adventurer if you have a warship, and you live in a desert.
You may be an adventurer if the prospect of owning a Returning Frost-Burst Caber is a Christmas list item.
If you have ever played WHEEL OF REINCARNATION with the town folk of a village till one came back as something useful to crossbreed a dragon with. Then you may be an adventurer.
If you offer to settle a tavern tab by clearing out the owners basement of vermin.
If you offer to settle a tavern tab by promising not to plunder his daughters *cough*
If you offer to settle a tavern tab by promising TO plunder his daughters *wink*
You consider a portable hole full of gold coins "Fun for kids" but somehow forget how deep it is.
There's a town named after you, the people in it are all named after you, and every morning you shout their name out. The last one to arrive is forced to bath you. You may not be an adventurer, but you retired.
You call Tiamat, "Fluffy."
You have your deity on speed dial, your patron on edge, and your wives on a wagon.