The meaning of the poem is a prayer for God to restore the speaker's heart from the barren and desolate. He wants to feel anything other than empty and miserable.

At the beginning of the poem, the speaker says his heart is arid and that the rain hasn't come. Arid ground is dry, cracked, and not nourished with rain. He goes on to say that the horizon is barren as well. Every indication points toward the speaker feeling empty and flat. It's almost like he doesn't have the ability to feel an emotion—even a bad one.

This is more clear when he asks God to even send a violent thunderstorm to quench his heart. Anything is better than being barren and empty. He doesn't even mind the violence of lightning as long as the "pervading silent heat" is gone.

He ends the poem by asking God to give him grace.

The poet in song 40 in "The Gitanjali," by Tagore, is in the mood of despair. We don't know this at the start of the poem, where the poet is asking God to rain on his "arid heart." He doesn't even care if the rain comes in the form of a fierce storm; he just needs relief.

"Send thy angry storm, dark with death, if it is thy wish, and with lashes of lightning startle the sky from end to end."

All the poet desires is that his overwhelming despair, which burns within him, be drowned in a healing rain.

The final line of the poem is that last entreaty the poet makes to God—asking for both a cleansing wrath of the Father, and at the same, the tender heart of the Mother.

"Let the cloud of grace bend low from above like the tearful look of the mother on the day of the father's wrath."