What did roosevelt mean by the phrase freedom from want?

"Freedom from want" meant having an adequate standard of living, sufficient to meet daily needs.

Roosevelt included freedom from want in what has become known as his "Four Freedoms" speech, which was actually his 1941 State of the Union address.  The four freedoms he named as essential are freedom of speech, freedom of worship, freedom from want, and freedom from fear.  These were the things he deemed essential for all people in the world to have.  (Note that the speech was made during the time that World War II was raging and threatening such freedoms around the world.)

The right to an adequate standard of living (freedom from want) was also included in the Universal Declaration of Human Rights, a document adopted by the United Nations.  Eleanor Roosevelt, the president's wife, chaired the committee that produced that declaration.  You can gain a good idea of what President Roosevelt intended from what is stated in Article 25 of the Declaration:  Everyone has the right to a standard of living adequate for the health and well-being of himself and of his family, including food, clothing, housing and medical care and necessary social services, and the right to security in the event of unemployment, sickness, disability, widowhood, old age or other lack of livelihood in circumstances beyond his control.