Semtex rhymes with:
ashtec's, cortex, pantex, vortex, abex, albunex, alpex, ashtec's, avanex, cognex, complex, cortex, culex, dudeck's, forex, gemex, genex, ibex, immunex, index, inlex, koscheck's, micrografx, mondex, moulinex, ovex, pantex, patlex, proctorsilex, purex, quadrex, qualex, quanex, reflex, rolex, rorex, royex, simex, spinifex, timex, trizec's, uzbeks, vortex
Semtex sounds like:
saint's, saints, saints', san-diego, sand's, sandage, sandhog, sandhogs, sandidge, sandos, sandose, sandoz, sandoz's, sands, sandusky, sandwich, sandwiches, sandwick, sandy's, sanitize, santa's, santas, santiago, santos, santosh, santosuosso, santucci, sassnet's, sassnets, scents, schantz, schematic, schmidt's, schmidtke, schmitz, schmutz, schnittke, schnitz, schwantes, second's, seconds, segment's, segments, semantic, semantics, sematech, semiotic, semiotics, semitic, senate's, sendak, sends, sentz, shands, shandwick, shandwick's, shanties, shantz, shawmut's, shindig, shontz, shunts, simmonds, simonds, skinheads, smith's, smiths, smithwick, smits, smooths, smoots, smudge, snatch, snatches, snitch, snout's, snouts, sonatas, sondag, sonnets, sonntag, sontag, sound's, sounds, sumita's, summit's, summits, sundae's, sunday's, sundays, sundews, swantek, symantec, symantec's, symmonds, symonds, synod's, syntax, syntech, syntex, syntex's, syntheses, synthesis, synthesize, synthetic, synthetics