I've volunteered to put up a definition a day for a poetry list of which I am a member.
If you need to clear up any of the words in this definition, please do.
1. A composition designed to convey a vivid and imaginative sense of experience, characterized by the use of condensed language, chosen for its sound and suggestive power as well as its meaning, and by the use of such literary techniques as structured meter, natural cadences, rhyme, or metaphor.
-- there are several more definitions which I'll do in subsquent posts. But there's plenty to chew on here in definition #1.
Putting that in my own words for my own use:
A poem is something written to get across a clearly created feeling or beingness, usually using dense, carefully chosen words that sound right and carry layers of meaning, and possibly using meter, rhyming words, and drawing comparisons that illustrate what you're trying to get across.
Off the top of my head examples of poems that get across a feeling:
Renascence by Edna St. Vincent Millay (1892-1950)
Once by the Pacific by Robert Frost (1874-1963)
Do Not Go Gentle Into That Good Night by Dylan Thomas (1914-1953)
Examples of poems that get across a beingness:
My Last Dutchess by Robert Browning (1812-1899)
Many of the hauku by Matsuo Basho (1644-1694) convey a beingness:
Once again I will lean against
The autumn full moon:
All night long
I paced around the lake.
(More basic poetry definitions soon.)