xmaxima: 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/xmaxima - from package: maxima-gui

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

On Debian possible default full paths are:

/usr/bin/xmaxima - from package: xmaxima

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

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