Is it possible to gift into a previously set up disclaimer trust???

No. The Disclaimer Trust was intended to make use of any amount that you husband could pass free of estate taxes (or such lesser amount that you disclaimed). If you want to make a gift of the amount that you can pass free of estate and gift taxes, that gift needs to be made to a separate trust. Although your attorney is busy, he or she should be able to answer your questions.

The short answer is that you really need to consult your attorney about this. I am sure that you did your best in laying out the facts, but in order to answer your question we would need to know a lot more. Is your "gift" that portion of your husband's estate that is funding the disclaimer trust? Or, do you want to make a "gift" of some of your property to the disclaimer trust (for whatever reason)? Either way, it is something that requires further discussion with someone familiar with your estate plan. Unfortunately, that isn't us.

To answer your question, "is is possible to gift into the disclaimer trust?" you need to read the disclaimer trust agreement carefully to see if it allows for additional contributions. Probably the trustee has discretion whether to accept new contributions so you need to consult with the trustee. A more important question that you did not ask directly is "is it a good idea to make contributions to the disclaimer trust?" I join with the other two attorneys to urge you to consult with your attorney on this essential question. It is impossible for us to say without knowing your entire estate plan, your current situation and what you are trying to accomplish. Based on the facts that you gave, I could make some educated guesses but in this forum they will not be useful to you or anyone else. The list of assumptions would take up all of the remaining allowed space.

The purpose of a disclaimer trust is to received property from the deceased spouse to avoid it being taxed as part of the surviving spouse's estate when the surviving spouse dies in the future. The disclaimer trust only can be funded for a limited time to accomplish this purpose - the surviving spouse has to make a disclaimer election within 9 months from the date of the first spouse's death by filing a special tax form with the State and the IRS. Since your husband died 3 years ago you should have already done this. I would assume that you now want to gift property that is in your estate, most likely to your children, to avoid more estate tax when you die. One popular way to do this is with a Crummey trust where the child has a small window of time to remove the property before it becomes locked up in the trust. This removal period is necessary for the property to qualify as a completed gift. Smart children don't try to remove the property as a practical matter because they know that you will make subsequent gifts if they don't. You would need a separate trust to be drafted with this mechanisms which the disclaimer trust does not have nor was the disclaimer trust designed for this purpose. There are other devices to move property besides a trust. You need to meet with your attorney and discuss what you are trying to do and what your goals are.