What is the difference between the terms "liberal" and "progressive" in American politics?

[NRaleighLiberal]

5. Always an interesting discussion topic. Some dictionary definitions -

liberal

— adj
1. relating to or having social and political views that favour progress and reform
2. relating to or having policies or views advocating individual freedom
3. giving and generous in temperament or behaviour
4. tolerant of other people
5. abundant; lavish: a liberal helping of cream
6. not strict; free: a liberal translation
7. of or relating to an education that aims to develop general cultural interests and intellectual ability


progressive

— adj
1. of or relating to progress
2. proceeding or progressing by steps or degrees
3. ( often capital ) favouring or promoting political or social reform through government action, or even revolution, to improve the lot of the majority: a progressive policy
4. denoting or relating to an educational system that allows flexibility in learning procedures, based on activities determined by the needs and capacities of the individual child, the aim of which is to integrate academic with social development
5. Compare regressive (of a tax or tax system) graduated so that the rate increases relative to the amount taxed
6. (esp of a disease) advancing in severity, complexity, or extent
7. (of a dance, card game, etc) involving a regular change of partners after one figure, one game, etc
8. denoting an aspect of verbs in some languages, including English, used to express prolonged or continuous activity as opposed to momentary or habitual activity: a progressive aspect of the verb ``to walk'' is ``is walking.''

— n
9. a person who advocates progress, as in education, politics, etc
10. a. the progressive aspect of a verb
b. a verb in this aspect