Unlike other incarnations, Lord Sri Caitanya Mahaprabhu appears in this age of Kali as a devotee of the Lord. Therefore He is called a concealed or covered incarnation

Expressions researched:
"concealed descent" |"concealed incarnation"

SB Canto 5

In this age of Kali, the Supreme Personality of Godhead (Bhagavān) does not appear as a līlāvatāra, an incarnation to display pastimes. Therefore He is known as tri-yuga. Unlike other incarnations, Lord Śrī Caitanya Mahāprabhu appears in this age of Kali as a devotee of the Lord. Therefore He is called a concealed incarnation (channāvatāra).

SB 5.18.35, Translation and Purport:

O Lord, we offer our respectful obeisances unto You as the gigantic person. Simply by chanting mantras, we shall be able to understand You fully. You are yajña (sacrifice), and You are the kratu (ritual). Therefore all the ritualistic ceremonies of sacrifice are part of Your transcendental body, and You are the only enjoyer of all sacrifices. Your form is composed of transcendental goodness. You are known as tri-yuga because in Kali-yuga You appeared as a concealed incarnation and because You always fully possess the three pairs of opulences.

Śrī Caitanya Mahāprabhu is the incarnation for this age of Kali, as confirmed in many places throughout the purāṇas, the Mahābhārata, Śrīmad-Bhāgavatam and the Upaniṣads. The summary of His appearance is given in Caitanya-caritāmṛta (CC Madhya 6.99) as follows:

kali-yuge līlāvatāra nā kare bhagavān

ataeva 'tri-yuga' kari' kahi tāra nāma

In this age of Kali, the Supreme Personality of Godhead (Bhagavān) does not appear as a līlāvatāra, an incarnation to display pastimes. Therefore He is known as tri-yuga. Unlike other incarnations, Lord Śrī Caitanya Mahāprabhu appears in this age of Kali as a devotee of the Lord. Therefore He is called a concealed incarnation (channāvatāra).

CC Adi-lila

The Lord tried to conceal His identity as the Supreme Personality of Godhead by representing Himself as a devotee, but His pure devotees could recognize Him by His special features. The Vedas and Purāṇas foretell the appearance of Lord Caitanya, but still He is sometimes called, significantly, the concealed descent of the Supreme Personality of Godhead.

CC Adi 3 Summary:

In this chapter the author has fully discussed the external reasons for the descent of Śrī Caitanya Mahāprabhu. The Supreme Personality of Godhead, Lord Śrī Kṛṣṇa, after displaying His pastimes as Lord Kṛṣṇa, thought it wise to make His advent in the form of a devotee to explain personally the transcendental mellows of reciprocal service and love exchanged between Himself and His servants, friends, parents and fiancīes. According to the Vedic literature, the foremost occupational duty for humanity in this Age of Kali is nāma-saṅkīrtana, or congregational chanting of the holy name of the Lord. The incarnation for this age especially preaches this process, but only Kṛṣṇa Himself can explain the confidential loving service performed in the four principal varieties of loving affairs between the Supreme Lord and His devotees. Lord Kṛṣṇa therefore personally appeared, with His plenary portions, as Lord Caitanya. As stated in this chapter, it was for this purpose that Lord Kṛṣṇa appeared personally in Navadvīpa in the form of Śrī Kṛṣṇa Caitanya Mahāprabhu.

Kṛṣṇadāsa Kavirāja has herein presented much authentic evidence from Śrīmad-Bhāgavatam and other scriptures to substantiate the identity of Lord Caitanya with Śrī Kṛṣṇa Himself. He has described bodily symptoms in Lord Caitanya that are visible only in the person of the Supreme Lord, and he has proved that Lord Caitanya appeared with His personal associates-Śrī Nityānanda, Advaita, Gadādhara, Śrīvāsa and other devotees-to preach the special significance of chanting Hare Kṛṣṇa. The appearance of Lord Caitanya is both significant and confidential. He can be appreciated only by pure devotees and only through the process of devotional service. The Lord tried to conceal His identity as the Supreme Personality of Godhead by representing Himself as a devotee, but His pure devotees could recognize Him by His special features. The Vedas and Purāṇas foretell the appearance of Lord Caitanya, but still He is sometimes called, significantly, the concealed descent of the Supreme Personality of Godhead.