| | Txt words we should all know for O |
| | 121 | | one to one |
| | 121 | | one-2-one |
| | 143 | | one hundred and forty three |
| | 1FTR | | one for the road |
| | 1ns | | once |
| | 1ns | | ones |
| | 1TL | | one true love |
| | Dad@hvn | | our father who art in heaven |
| | fo | | of |
| | hav | | ocean |
| | kthxbye | | ok, thank you, goodbye |
| | kthxbye | | okay thanks goodbye |
| | O1 | | only one |
| | O2 | | ohto |
| | O2 | | oxygen |
| | o4u | | only for you |
| | oap | | old age pensioner |
| | oap | | old age person |
| | oap | | old aged pensioners |
| | oap | | old fart |
| | oap | | old person |
| | oap | | old timer |
| | oap | | old-timer |
| | OBTS | | once bitten twice shy |
| | obtw | | oh by the way |
| | obtw | | oh, by the way |
| | ocup8n | | occupation |
| | Oh2 | | Oh too |
| | OIC | | oh I see |
| | OIC | | oh, I see |
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