Another word for firmly
Not easily moved
immovably, solidly, rigidly, stably, fast, tight, tightly, fixedly, durably, enduringly, substantially, securely, heavily, sturdily, stiffly, inflexibly, unshakably, soundly, strongly, steadily, solid as a rock*, like the Rock of Gibraltar*, there for all time*.
Antonyms loosely, tenuously, insecurely.
resolutely, steadfastly, doggedly, stolidly, tenaciously, determinedly, staunchly, adamantly, constantly, intently, purposefully, obdurately, persistently, obstinately, stubbornly, perseveringly, pertinaciously, unwaveringly, unswervingly, unchangeably, indefeasibly, with a heavy hand, through thick and thin*.