Solaris comes with a nifty tool to help deal with zombies (no, they don’t ship you a shotgun with your media kit), and it comes by the name preap. To use preap, you can pass it the PID of the zombie process you want to reap:

$ ps -ef | grep defunct

    root   646   426   0        - ?           0:00 
    root  1489 12335   0 09:32:54 pts/1       0:00 grep defunct

$ preap 646
646: exited with status 0

This will cause the process to exit, and the kernel can then free up the resources that were allocated by that process.