A java applet called JavaGismu allows you to interactively browse the gismu list and see the english translation. There is a screenshot.
I have made a jar of the applet which will allow you to run it as an application. You will also need to download gismu.gz, a compressed version of the gismu list.
On my (linux) computer I just make sure the swing.jar is my CLASSPATH variable and use the JDK directly:
/usr/jdk118/bin/appletviewer http://lojban.sourceforge.net/JavaGismu/applet_test.html
java -cp javagismu.jar org.lojban.javagismu.JavaGismu
It searches by gismu and the 3 rafsi fields. It doesn't match only the beginning of the word, but any substring.
When you click on a result it shows you the meaning, place structure and also creates buttons to cross-reference other gismu.
You can select to search by a specific rafsi as well if you need to.