How to type a grave accent (aka ` backtick ` ) in markdown?

From the Code section of the Markdown syntax page:

To include a literal backtick character within a code span, you can use multiple backticks as the opening and closing delimiters:

``There is a literal backtick (`) here.``

For example,

``hello `amazing` world``

renders as

hello `amazing` world

Edit: Re-reading this, I wonder if you want to use single backticks outside of code blocks. You should be able to backslash-escape them:

Markdown allows you to use backslash escapes to generate literal characters which would otherwise have special meaning in Markdown’s formatting syntax…

Markdown provides backslash escapes for the following characters:

\   backslash
`   backtick
*   asterisk
_   underscore
{}  curly braces
[]  square brackets
()  parentheses
#   hash mark
+   plus sign
-   minus sign (hyphen)
.   dot
!   exclamation mark

This works on Stack Overflow, e.g.

hello \`amazing\` world

renders as

hello `amazing` world

If this doesn't work you'll have to provide more information about the Markdown processor you're using.