mesongui: 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 Debian possible default full paths are:

/usr/bin/mesongui - from package: meson-gui

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

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