Question

what do you mean by conspicuous nucleus?

Answer 1

The nucleus which is prominent and easily stand out when we observe the respective structure of a cell.
e.g from the mount of onion we can easily distinguish between the nucleus and the cytoplasm.

Answer 2

When you make a temporary mount of onion peel or cheek cell you can distinguish the cytoplasm and so the nucleus can be called conspicuous nucleus in this case