  Magnetar giant flares are rare and highly energetic phenomena observed in the
transient sky whose emission mechanisms are still not fully understood.
Depending on the nature of the excited modes of the magnetar, they are also
expected to emit gravitational waves, which may bring unique information about
the dynamics of the excitation. A few magnetar giant flares have been proposed
to be associated to short gamma-ray bursts. In this paper we revisit, with a
new gravitational-wave search algorithm, the possible emission of gravitational
waves from four magnetar giant flares within 5 Mpc. While no gravitational-wave
signals were observed, we discuss the future prospects of detecting signals
with more sensitive gravitational-wave detectors. We in particular show that
galactic magnetar giant flares that emit at least 1% of their electromagnetic
energy as gravitational waves could be detected during the planned observing
run of the LIGO and Virgo detectors at design sensitivity, with even better
prospects for third generation detectors.
