I copied and pasted the definition I found by clicking on the word "attainder" in the constitutiion on line.
There is a glossery with the words defined as was intended by the original constitution.
http://www.usconstitution.net/const.html
Other sources suggest a more limited definition that “negative effects.
>>’’Bills of attainder . . . are such special acts of the legislature, as inflict capital punishments upon persons supposed to be guilty of high offences, such as treason and felony, without any conviction in the ordinary course of judicial proceedings. If an act inflicts a milder degree of punishment than death, it is called a bill of pains and penalties. . . . In such cases, the legislature assumes judicial magistracy, pronouncing upon the guilt of the party without any of the common forms and guards of trial, and satisfying itself with proofs, when such proofs are within its reach, whether they are conformable to the rules of evidence, or not. In short, in all such cases, the legislature exercises the highest power of sovereignty, and what may be properly deemed an irresponsible despotic discretion, being governed solely by what it deems political necessity or expediency, and too often under the influence of unreasonable fears, or unfounded suspicions.’’ 1701 The phrase ‘’bill of attainder,’’ as used in this clause and in clause 1 of Sec. 10, applies to bills of pains and penalties as well as to the traditional bills of attainder. 1702 <<
http://caselaw.lp.findlaw.com/data/constitution/article01/47.html