gajim: 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/gajim - from package: gajim

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

On Debian possible default full paths are:

/usr/bin/gajim - from package: gajim

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

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