This is another Catholic definition of apocryphal gospels (emphasis mine):
(1) APOCRYPHAL GOSPELS
The term apocryphal in connection with special Gospels must be understood as bearing no more unfavourable an import than “uncanonical”. This applies to the Gospel of the Hebrews and in a less degree to that of the Egyptians, which in the main seem to have been either embodiments of primitive tradition, or a mere recasting of canonical Gospels with a few variations and amplifications. It is true, all the extant specimens of the apocryphal Gospels take the inspired evangelical documents as their starting-point. But the genuine Gospels are silent about long stretches of the life of Our Lord, the Blessed Virgin, and St. Joseph. Frequently they give but a tantalizing glimpse of some episode on which we would fain be more fully informed. This reserve of the Evangelists did not satisfy the pardonable curiosity of many Christians eager for details, and the severe and dignified simplicity of their narrative left unappeased imaginations seeking the sensational and the marvellous. When, therefore, enterprising spirits responded to this natural craving by
pretended Gospels full of romantic fables and fantastic and striking details, their
fabrications were eagerly read and largely accepted as true by common folk who were devoid of any critical faculty and who were predisposed to believe what so luxuriously fed their pious curiosity. Both Catholics and Gnostics were concerned in writing these
fictions. The former had no other motive than that of a
pious fraud, being sometimes moved by a real though misguided zeal, as witness the author of the Pseudo-Matthew: Amor Christi est cui satisfecimus. But the heretical apocryphists, while gratifying curiosity, composed
spurious Gospels in order to trace backward their beliefs and peculiarities to Christ Himself. The Church and the Fathers were hostile even towards the narratives of orthodox authorship. It was not until the Middle Ages, when their true origin was forgotten even by most of the learned, that these apocryphal stories began to enter largely into sacred legends, such as the “Aurea Sacra”, into miracle plays, Christian art, and poetry. A comparison of the least extravagant of these productions with the real Gospels reveals the chasm separating them. Though
worthless historically, the apocryphal Gospels help us to better understand the religious conditions of the second and third centuries, and they are also of no little value as early witnesses of the canonicity of the writings of the four Evangelists. The quasi-evangelistic compositions concerning Christ which make no pretensions to be Gospels will be treated elsewhere. They are all of orthodox origin. (See AGRAPHA.)
newadvent.org/cathen/01601a.htm#III
