what is to print a character on top of another

[Derek64]

what is to print a character on top of another

[boxtops]

overlay ? - or do you mean like adding an accent over a letter, like é ?

[methyl]

overstrike

[MarkRae]

Superimpose?

[kolumkille]

overwrite

[methyl]

Could equally be overtype, but the old term from typewriter days is overstrike. When you are crossing something out, it becomes strikethrough .

None of these three words are in Chambers without a hyphen or space character.

[factor-fiction]

Is this a crossword clue? If so, please can you tell us the number of letters?

[boxtops]

Here's the full clue, from another post http://www.theanswerb.../Question1148225.html