Senses
信马由缰/ 信馬由韁 to ride with loose reins
To let a horse wander at will while riding without pulling on the reins
信马由缰/ 信馬由韁 to lack one's own opinion
To have no fixed opinion and allow oneself to be led by others or by circumstances.
信马由缰/ 信馬由韁 to stroll aimlessly
To wander or act without a specific purpose or plan, or to give free rein to something such as one's imagination