What does this mean

[JenB]

Not on Ancestry, see my edit

OK I'll re-phrase.

It seems to me that the bit after the word miner is in a different hand.

[ainslie]

There is usually a classification of occupations.  If the return form stated plain 'miner', someone may have queried whether it was of coal or something else, but in the absence of details, the later hand has added words to explain that it was not defined.
My view, for what it's worth.
A

[stanmapstone]

This another entry from the 1881 Census where 'under' or 'undefined' has been added by the clerk extracting occupations. Transcribed as Miner ( Under Gr)
Stan

[Redroger]

Before I saw Stan's final post I thought the entry was made when the form was processed. For what it's worth doesn't undefined mean it was unknown whether he was a surface or underground worker?

[stanmapstone]

I think it means 'undefined' as no mineral is specified. This is from the Instructions to the clerks employed in classifying the occupations of the people, in the 1881 Census. All Miners are in Order 21 Sub-order 1 or Sub-Order 3. There is no differentiation between surface and underground.
Stan

Edited

[cardiff]

Hey stanmapstone
 Thanks for that you learn something  new every day
Thank you for taking the time and making the effort
cheers cardiff 

[stanmapstone]

Not on Ancestry, see my edit

OK I'll re-phrase.

It seems to me that the bit after the word miner is in a different hand.

If the schedule just had 'Miner' then when the enumerator was copying the schedule he could have added 'undef'? or it could have been the clerk in the census office extracting the occupations, in which case it would be in a different hand. Usually annotations made in the census office were in a different colour, but, of course, this would not show on the image.

Stan

[Redroger]

If the clerk knew the area involved he could probably make an educated guess as to the type of miner, but if he was a civil servant in London, undefined had to stay at that I would think.

[stanmapstone]

He was patient  in Kings College Hospital, London.

Stan