wnb: 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/wnb - from package: wordnet

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

On Debian possible default full paths are:

/usr/bin/wnb - from package: wordnet-gui
/usr/share/wordnet/bin/wnb - from package: wordnet-gui

You may install the required package with command apt-get install {package}

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