Meaning and local context
In Manchester, “mither” means To bother, pester, worry, or make a fuss. A familiar Mancunian and northern English verb or noun.
Example in context
A local example is “Stop mithering me while I finish this.” In plain English, that means “Stop bothering me while I finish this.”
Stop mithering me while I finish this.
Stop bothering me while I finish this.
How to interpret it
The surrounding sentence is important when interpreting “mither”. Use the regional sense above when the situation matches the example instead of relying on the word or phrase in isolation.
Tone and caution
It can sound sharper than playful teasing. Because this is informal regional language, tone and situation should guide whether you use “mither” yourself or simply recognise it when someone else uses it.