i Register
In some senses, undertime is marked as informal, obsolete. Watch for register when choosing this word.
verb
To measure wrongly, so that it seems to take less time than actually required.
To underexpose.
noun
The time spent at a workplace doing non-work activities.
noun
The later part of the day; afternoon; undertide.
He, comming home at undertime, there found / The fayrest creature, that he euer saw, / Sitting beside his mother on the ground; / The sight whereof did greatly him adaw.