Ubuntu 14.10, Unity, running Windows under KVM. Pressing Ctrl+Altimmediately causes the focused window to maximise vertically (no other keys pressed).
Pressing them again causes the window to toggles between that and maximise in both dimensions. A double click in the title bar maximises (if not already so), and another double click restores the window to its original dimensions.
I have found no binding for simply Ctrl+Alt in Settings→Keyboard→Shortcuts. I also tried CompizConfig settings manager, found no references to Ctrl+Alt
The output of
gsettings list-recursively | grep --ignore-case ctrl | grep --ignore-case alt
gsettings list-recursively | grep --ignore-case ctrl | grep --ignore-case alt
to paste.ubuntu.com and post the link you receive back into your question? Edit your question first.org.gnome.settings-daemon.plugins.media-keys window-screenshot-clip <Ctrl><Alt>Print org.gnome.settings-daemon.plugins.media-keys screencast <Ctrl>
<Shift><Alt>R org.gnome.settings-daemon.plugins.media-keys window-screenshot-clip '<Ctrl><Alt>Print' org.gnome.settings-daemon.plugins.media-keys screencast <Ctrl><Shift><Alt>R org.onboard.lockdown disable-keys [[CTRL', LALT, F[0-9]+]] org.onboard.lockdown disable-keys [[CTRL', LALT, F[0-9]+]]`find ~ -type f -maxdepth 2 -print0 -iname '.*'| xargs -0 grep -rIP 'Alt_(L|R)'
to check your configuration files and add the output into your question as an edit. After that give me a ping with @A.B. in the comments.