To understand what that experience was, what happened in there (by which I mean both "in the meditation cave" and "in me") brings up a topic rather esoteric and wild—namely, the subject of kundalini shakti.
Every religion in the world has had a subset of devotees who seek a direct, transcendent experience with God, excusing themselves from fundamentalist scriptural or dogmatic study in order to personally encounter the divine. The interesting thing about these mystics is that, when they describe their experiences, they all end up describing exactly the same occurrence. Generally, their union with God occurs in a meditative state, and is delivered through an energy source that fills the entire body with euphoric, electric light. The Japanese call this energy ki, the Chinese Buddhists call it chi, the Balinese call it taksu, the Christians call it The Holy Spirit, the Kalahari Bushmen call it n/um (their holy men describe it as a snakelike power that ascends the spine and blows a hole in the head through which the gods then enter). The Islamic Sufi poets called that God-energy "The Beloved," and wrote devotional poems to it. The Australian aborigines describe a serpent in the sky that descends into the medicine man and gives him intense, otherworldly powers. In the Jewish tradition of Kabbalah this union with the divine is said to occur through stages of spiritual ascension, with energy that runs up the spine along a series of invisible meridians.
Saint Teresa of Avila, that most mystical of Catholic figures, described her union with God as a physical ascension of light through seven inner "mansions" of her being, after which she burst into God's presence. She used to go into meditative trances so deep that the other nuns couldn't feel her pulse anymore. She would beg her fellow nuns not to tell anyone what they had witnessed, as it was "a most extraordinary thing and likely to arouse considerable talk." (Not to mention a possible interview with the Inquisitor.) The most difficult challenge, the saint wrote in her memoirs, was to not stir up the intellect during meditation, for any thoughts of the mind—even the most fervent prayers—will extinguish the fire of God. Once the troublesome mind "begins to compose speeches and dream up arguments, especially if these are clever, it will soon imagine it is doing important work." But if you can surpass those thoughts, Teresa explained, and ascend toward God, "it is a glorious bewilderment, a heavenly madness, in which true wisdom is acquired." Unknowingly echoing the poems of the Persian Sufi mystic Hafiz, who demanded why, with a God so wildly loving, are we not all screaming drunks, Teresa cried out in her autobiography that, if these divine experiences were mere madness, then "I beseech you, Father, let us all be mad!"
Then, in the next sentences of her book, it's like she catches her breath. Reading Saint Teresa today, you can almost feel her coming out of that delirious experience, then looking around at the political climate of medieval Spain (where she lived under one of the most re-pressive religious tyrannies of history) and soberly, dutifully, apologizing for her excitement. She writes, "Forgive me if I have been very bold," and reiterates that all her idiot babbling should be ignored because, of course, she is just a woman and a worm and despicable ver-min, etc., etc. You can almost see her smoothing back her nun's skirts and tucking away those last loose strands of hair—her divine secret a blazing, hidden bonfire.