wishwn: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/wishwn - from package: wordnet

You may install the required package with command yum install {package}

Error in other languages:
wishwn: bevel nie gevind nie
wishwn: comandă negăsită
wishwn: comando não encontrado
wishwn: commande introuvable
wishwn: command not found
wishwn: käsku ei ole
wishwn: không tìm thấy lệnh
wishwn: komanda nerasta
wishwn: Kommando nicht gefunden.
wishwn: kommandot finns inte
wishwn: komut yok
wishwn: nie znaleziono polecenia
wishwn: níor aimsíodh an t-ordú
wishwn: no se encontró la orden
wishwn: no s'ha trobat l'ordre
wishwn: opdracht niet gevonden
wishwn: parancs nem található
wishwn: perintah tidak ditemukan
wishwn: príkaz nenájdený
wishwn: příkaz nenalezen
wishwn: команда не найдена
wishwn: командата не е открита
wishwn: 命令找不到
wishwn: コマンドが見つかりません