I've added this to my
nnoremap <C-S-w> :tabclose<CR>, and it works!
But my problem is that CTLR+w closes the terminal tab as well, ignoring the shift key specified in the above rule. So it will conflict with the window commands, such as
CTLR+w, v (instead of splitting the window, as soon as I hit CTLR+w it tries to close a tab).
:verbose map <c-w> says there are no other conflicting mappings.
Although it must be irrelevant to the terminal (because
<c-w> is showing a behavior internal to vim(closing a vim tab), I've also de-configured all the
ctrl+ws from my terminal's configuration, but it's still not working as expected.