Can't plot with gnuplot on my Mac
The same thing happened to me, but then I ran 

brew uninstall gnuplot; brew install gnuplot --with-x11


and installed XQuartz. Now gnuplot supports the x11 terminal:



You can also save the output to a file and use qlmanage -p:

gnuplot -e 'set term png; set output "/tmp/plot.png"; plot sin(x)'; qlmanage -p /tmp/plot.png


qlmanage -p shows a sandboxing error in 10.9 and prints some unnecessary text to STDOUT, so I use a function like ql() { qlmanage -p "$@"&amp;&gt;/dev/null; } in shells.

A third option is to use set term dumb for plain text output.