Warren as restless questioner; Rumor Verified, by Robert Penn Warren. New York: Random House. 97 pp. $9.95.

With all his honors on, Robert Penn Warren is something of the grand old man of American letters. Novelist, poet, dramatist, critic, and teacher, he has won the Pulitzer Prize for both fiction and poetry. His ''Selected Poems'' won the Bollingen Prize in 1967. He has received the National Book Award, and most recently was recipient of a MacArthur Prize Fellowship. Plus more.

His latest volume of poems, ''Rumor Verified,'' shows Warren still in there competing. Of the many roles the poet plays for us, RPW occupies several. He is the namer and the teller. He is the watchman of the night, the doubter, the preserver of fugitive moods and moments. Mostly in this current series Warren is the restless questioner.

A typical poem finds him lying abed in the early dawn, thinking back over his past, and contemplating ''the tales and contortions of Time.'' In later life, a man is given to reflect: ''Was this the life that all those years I lived, and did not know?'' To Warren, reclining in an after midnight hour, ''Whatever pops into your head . . . may do to make a poem . . . every accident yearns to be more than itself, yearns . . . to participate in the world's blind, groping rage toward meaning.'' What does life tell us? What does it mean?

Warren is preoccupied with the rage toward meaning. He hovers between ponderous abstraction and vivid concretion, studies to ''see how the dream . . . strives to decode the clutter of our lives.''

In his cluttered life the poet has walked mountain trails and observed the distant stream that ''uncoils like a glittering wire tangled in stone-slots.'' He has driven West into the setting sun and had a pheasant fly into his windshield. He has stood on the street corner at midnight in New York City and felt ''a pang of despair, like nausea.'' He has loved. He has fathered children. He has seen boyhood friends grow old and has forgotten their names. He has known ''the mystery of love's redeeming smile.''

In short, if the poet's life means anything, it means live and endure and love.

Now, late in that life, he gives us another harvest of barberries, red-fruited, of clouds curdled in a skim-milk blue sky, and black earth studded with the bright gold stars of rain-summoned chanterelles. The poet, watcher of the world's pulse, grows wan with fear and trembling, wavers as the night seems long, but wakes again at crocus dawn to the benediction of another day of spring and returning light.

Like the poetic talents of Thomas Hardy and Robert Frost, RPW's gift goes on giving him strong characteristic poems that testify to the power of his craft and that ''call on life to be lived gladly, gladly.''