Hi Dragon lady,
Here is a banking definition: "Altered Item / Fictitious Item - A check returned stamped Altered, or stamped Fictitious item does not match the account holder's records or the bank's records as far as the amount, date or terms of the check and is being returned in dispute of its validity.
An Example would be:
This can be something as simple as someone writing a check for $125.99 and then changing the 5 in 125 to a 6 to make the check $126.50. Any alteration can void the check at the digression of the bank. A cross out, alteration or change should be initialed by the account holder, but does not always stop returns, especially with high dollar items. This stamp, Altered Item, or Fictitious item can also come with forged money orders, forged cashier's checks, and forged traveler's checks.
For future information you can look at: http://checkwriter.net/returned-check.htm