Synonyms for Solid:

adj.

cohesive (adjective)
indissoluble, tough, congruous, connected, integrated, indivisible, consistent, conforming, cohesive, continuous, inseparable.
complete (adjective)
comprehensive, through, finished, full, complete, unabridged, sum, done, universal, collective, whole, thorough, unsevered, total, all, intact, entire, final, exhaustive, undivided, unified, conclusive, accomplished, uncut, integral, plenary.
continuous (adjective)
consecutive, regular, uninterrupted.
continuous, complete (adjective)
unanimous, undivided, steady, regular, uninterrupted, united, consecutive, unbroken.
dense (adjective)
dense, opaque, impenetrable, thick, compact, cohesive.
dependable, reliable (adjective)
pure, stalwart, good, trusty, trustworthy, valid, cogent, worthy, satisfying, real, constant, upstanding, genuine, steadfast.
effective (adjective)
cogent.
hard (adjective)
firm, stiff, rigid, callous, hard.
hard, dimensional (adjective)
dense, physical, tight, rooted, stable, thick, fixed, sound, set, substantial, firm, concrete, compact, material, strong, sturdy.
large (adjective)
massive.
material (adjective)
objective, concrete, palpable, natural, tangible, substantial, physical, corporeal, material, real, worldly.
precise (adjective)
accurate.
real (adjective)
concrete, true, real, honest, factual, sincere, veritable, substantial, actual, tangible, authentic, genuine.
reliable (adjective)
dependable, reliable, trustworthy.
rocklike (adjective)
hard.
similar (adjective)
homogeneous.
solid (adjective)
hard, set, firm, dense, stable, substantial, concrete, physical.
stable (adjective)
durable, permanent, continuous, stable, set, steady, changeless, firm, invariable, immovable, consistent, steadfast, constant, persistent.
strong (adjective)
heavy-duty.
substantial (adjective)
real, important, palpable, meaningful, material, appreciable, sturdy, substantial, physical, tangible, bodily, united, actual, considerable, firm, immanent, substantive, significant.
thick (adjective)
jellied.
united (adjective)
congruent, single, indivisible, integrated, coincident, complete, same, elemental, undivided, cohesive, unified, simple, united, uniform, coherent, irreducible, fundamental, homogeneous, holistic, intact, integral, congruous, atomic, entire, monolithic, pure.
well-founded (adjective)
well-founded.

n.

exact, perfect, resist, correct, unerring, strict, right, accurate, precise, specific, incompressible. continue, practical, mature, pragmatic, balanced, sure, Clear-headed, Grounded, realistic. bent, chunky, concentric, closed, just, aerodynamic, well-grounded, angular, well-founded, tight, bulbous, valid, cogent, clean, reason, concave, asymmetrical. medium, responsible, matter, trust, substance, trusty, agent, wax, reliable, powder, concentrate, trustworthy, dependable, stuff. beefy, brawny, big, built, agree, burly, coltish, barrel-chested, bullnecked. solid as a rock, tough, stubborn, heavy-duty, irresistible. figure, formation, shape, silhouette, proportions, physique, form, frame, build, profile. rock-hard, packed, inflexible, impenetrable. loyal (noun)
stalwart, faithful, diehard, committed.
solid (noun)
hearty, solidness, honourable, substantial, frozen, opaque, unhollowed, sound, massive, dry, jelled, solid-state, coagulated, homogenous, cubic, plain, jellied, congealed, concrete, unanimous, hard, self-colored, upstanding, unbroken, semisolid, wholesome, good, undiversified, unvaried, solidified, homogeneous, three-dimensional, worthy, noble, strong, satisfying, firm, honorable, unpatterned, self-coloured.
sound (noun)
good.

Other synonyms:

inflexible, oblique, harsh, dependable, stubborn, well-founded, cogent, matter. responsible, medium. stuff. agent, just, parallel. tight. firm
fixed.
loyal
stalwart, faithful, diehard, committed.
matter of fact
practical.
Other relevant words:
unfailing, good, valid, massive, dependable, responsible, tough, unanimous, well-founded, well-grounded, reliable, fixed, strong, sound, faithful.