If you own an IRA account, you will usually name a person as beneficiary to receive the IRA at the time of your death. In most instances, the beneficiary can roll the IRA over into an IRA in the beneficiary's name and also defer taxes by withdrawing the funds over time. When a beneficiary is a responsible adult and when you want that person to be able to access the full IRA account, this is a good plan. The IRA can be rolled over into an inherited IRA and the beneficiary can withdraw the funds over time, thereby reducing taxes. The person can also name a beneficiary for the IRA to go to upon his or her death. In a situation where spouses have been married for a long time and have responsible adult children together, this works well.
A traditional IRA is what is considered a "qualified" account. In essence, this means that the account gets special tax treatment---in particular, allowing you to defer taxation until a later date. With these types of accounts, you do not have to withdraw the money all at once. Many advisors refer to this as allowing you to "stretch" the distributions over time. Ultimately, this allows you to reduce income taxes which you must pay.
One definition of "disclaim" is when a person denies or renounces a claim to some thing or some right. In the context of estate administration, when a person disclaims, they are renouncing part or all of their right to receive under a Will, Trust or by operation of law.