| ossigenare | bleach |
| ossigenazione | oxygenation |
| ossigeno | oxygen |
| ossigeno disciolto | dissolved oxygen |
| ossimoro | contradiction in terms |
| Ossingen | Ossingen |
| Ossirinco | Oxyrhynchus |
| ossisulfuro di carbonio | carbonyl sulfide |
| Ossitocina | Oxytocin |
| osso | bone |
| osso a forchetta | wishbone |
| Osso buco | Ossobuco |
| osso duro | tough customer |
| osso pubico | pubis |
| osso sacro | sacrum |
| ossobuco | marrowbone |
| Ossola | Ossola |
| Ossuccio | Ossuccio |
| ossuto | bony |
| OST | OST |
| ostacolare | balk |
| ostacoli | fetter |
| ostacolista | hurdler |
| ostacolo | barrier |
| ostaggio | hostage |
| Ostalbkreis | Ostalbkreis |
| Ostalgie | Ostalgie |
| Ostasiengeschwader | German East Asia Squadron |
| Osteichdsethyes | Osteichthyes |
| Osteichthyes | Osteichthyes |
| ostello | hostel |
| ostello della gioventù | youth hostel |
| Ostelsheim | Ostelsheim |
| Osten | Osten |
| Ostenda | Ostend |
| Ostensivo | Airline codes |
| ostensorio | monstrance |
| ostentare | show off |
| ostentatamente | ostentatiously |
| ostentativo | ostentatious |
| ostentatore | flamboyant |
| ostentazione | gaudiness |
| Osteoderma | Osteoderm |
| Osteointegrazione | Osseointegration |
| Osteolaemus tetraspis | Dwarf Crocodile |
| osteologa | osteopath |
| Osteoporosi | Osteoporosis |
| Osterberg | Osterberg |
| Osterburken | Osterburken |
| Osterhofen | Osterhofen |
| osteria | crikey |
| Osteriggio | Spire light |
| Ostermundigen | Ostermundigen |
| Osterzell | Osterzell |
| Osterøy | Osterøy |
| ostetrica | obstetrician |
| ostetricia | obstetrics |
| ostetrico | obstetric |
| Ostfildern | Ostfildern |
| Ostfildern-Ruit | Ostfildern-Ruit |
| Ostfälisch | Eastphalian language |
| Ostheim vor der Rhön | Ostheim |
| Osthofen | Osthofen |
| ostia | host |
| Ostia Antica | Ostia |
| Ostiachi | Khanty people |
| Ostiglia | Ostiglia |
| ostile | adverse |
| Ostiliano | Hostilian |
| ostilità | opposition |
| ostinata | stubborn |
| ostinatamente | stubbornly |
| ostinatezza | obstinateness |
| ostinato | unwilling |
| ostinazione | persistence |
| Ostmark | Eastern March |
| Ostpolitik | Ostpolitik |
| Ostprignitz-Ruppin | Ostprignitz-Ruppin |
| Ostrach | Ostrach |
