Bhavocchvasa...means an outburst of feeling which expresses the bhava hidden in the hearts of the gopis. How does this occur?
The gopis were silent and Krsna was silent. They were feeling the mood of separation. The gopis were weeping and feeling very distressed at heart. But suddenly Krsna approached Srimati Radhika from behind and clasped His hands in front of Her eyes. She knew it was Him by the touch of Hish hands, but She did not let on that She knew. She exclaimed, "Visakha," and Krsna laughed, trying to restrain Himself.
Srimati Radhika was feeling overjoyed. Then just to increase Krsna's mood, She said, "Yes, I know. You are Lalita."
Then Krsna could not check Himself anymore and He at once began to laugh very loudly. Then Srimati Radhika said, "Oh You, You, You, You!" After this They embraced.
This is an example of bhavocchvasa.Srimati Radhika is always experiencing bhava within Her heart. But if an uddipana comes and makes these moods come out from the heart so that everyone can see, it is called bhavocchvasa.
This bhavocchvasa is so powerful that it cannot be checked by anything, just as the flow of a swift-moving river cannot be checked."
- from Gurudeva's commentary on Mahaprabhu's Siksastakam, at the end of the book Sri Siksastaka