There are many tracts on meditation in the context of different Hindu or Buddhist schools. These schools favour different styles of meditation. IMO all subscribe to Patañjali’s definition at the begin of his Yoga sutras as a common denominator of meditation:

"Yogaś citta-vritti-nirodhaḥ" (Yoga is stilling the fluctuations of the mind)

The Sanskrit योग (= yoga) in its broad sense means “any simple act or rite conducive to Yoga or abstract meditation”  (Monier-Williams)

From the viewpoint of psychology meditation is a method to induce an altered state of consciousness. The latter is an umbrella term covering in a neutral way a variety of mental states. For an introduction and pointer to the specialist literature see altered state of consciousness.

There are many tracts on meditation in the context of different Hindu or Buddhist schools. These schools favour different styles of meditation. IMO all schools subscribe to Patañjali’s definition at the beginning of his Yoga sutras as the common denominator of meditation:

"Yogaś citta-vritti-nirodhaḥ" (Yoga is stilling the fluctuations of the mind)

The Sanskrit योग (= yoga) in its broad sense means “any simple act or rite conducive to Yoga or abstract meditation”  (Monier-Williams)

From the viewpoint of psychology meditation is a method to induce an altered state of consciousness. The latter is an umbrella term covering in a neutral way a variety of mental states. For an introduction and pointer to the specialist literature see altered state of consciousness.