A semi-active device is used to damp vibrations moving relative to two elements between which the device is fixed. This device includes: a first member extending axially along a longitudinal axis; a second member extending axially along the same longitudinal axis, the two members being guided translatably relative to one another; a friction element extending between the two members and connecting them completely to each other by friction in an axial translational direction for any force below a threshold ‘s’, the force tending to create a relative translational movement of the two members along the longitudinal axis; an adjustment device enabling the value of the threshold to be adjusted. Thus adjusting the slip threshold of the friction element enables the dissipation conditions to be adjusted.