substandard

inferior

Of lower rank

• shoddyOf poor craftsmanship
• second-rateBelow acceptable standards
• low-gradeOf poor quality

mediocre · subpar · third-rate · suboptimal · cheap · deficient · unsatisfactory · crummy · lousy · shabby

faulty

Having defects or errors

• defectiveHaving inherent faults
• flawedHaving faults or imperfections
• imperfectHaving flaws or faults

damaged · blemished · marred · compromised · malfunctioning · broken · unreliable · irregular · rejected · seconds

shoddy

Of poor craftsmanship

• jerry-builtPoorly and hastily constructed
• ricketyUnsteady, liable to collapse
• flimsyWeak and easily damaged

ramshackle · dilapidated · decrepit · unsafe · condemned · unfit · makeshift · slipshod · crumbling · hazardous

inadequate

Not sufficient for purpose

• incompetentLacking necessary skill
• unacceptableNot meeting required standards
• unsatisfactoryNot good enough

lacking · insufficient · underperforming · disappointing · unqualified · amateurish · unprofessional · inept · subpar · wanting

slum

Impoverished urban district

• squalorDirty, degraded living conditions
• shantytownPoor area of crude shelters
• tenementMulti-unit urban dwelling

blight · overcrowded · unfit · condemned · dilapidated · rundown · ghetto · favela · hovel · flophouse

• "Sub-" wordssubway, submarine, subtract, subject, suburb
• academic failurefailing grade, failed test, F grade, flunk, flunking
• qualityquality, excellence, grade, caliber, superior
• inferiorinferior, second-rate, second-class, subpar, low-grade
• repair qualityflawless, professional, amateur, excellent, poor
• shoddinessslipshod, slapdash, hack job, botch job, botch