young and inexperienced person; greenhorn
Rare literary term; literally 'yellow beak', likening a young person to a fledgling bird. Not used in everyday conversation.
黄吻 is an old-fashioned word for a young, inexperienced person.
From 黄 (yellow) and 吻 (beak), referring to the yellow beak of a young bird, metaphorically extended to an inexperienced person. The exact historical origin is uncertain.