Rehash command

After removing the application in the directory listed in the $PATH variable, you may even see the command prompt when you type the first characters:

# pkg delete lsof
Checking integrity... done (0 conflicting)
Deinstallation has been requested for the following 1 packages (of 0 packages in the universe):

Installed packages to be REMOVED:
        lsof-4.90.b,8

Proceed with deinstalling packages? [y/N]: y
[1/1] Deinstalling lsof-4.90.b,8...
[1/1] Deleting files for lsof-4.90.b,8: 100%
# ls
ls        ls-F      lsextattr lsof      lspci     lsvfs

While running it will prompt "Command not found." definitely:

# lsof
lsof: Command not found.

Np matter install or remove application , you need to run rehash command in csh to causes the shell to recompute a table of where commands are located.

Reference:
Misc Tips & Tricks;
Rehash.