old man 
noun
1An elderly male person.He seemed to know of the book, but it's difficult to tell with old men, especially old men who don't get much company....
- It won't matter how young or old you are, our secret police enforcers are especially good at roughing up frail old men.
- In the park outside, an old olive grove, people dozed or picnicked under the trees, and a group of old men played boules.
Synonyms
senior citizen, pensioner, OAP, elder, elderly man, grandfather;
patriarch;
Scottish & Irish bodach
informal greybeard, gaffer, old codger, old boy, old chap, old geezer, old bloke, wrinkly
British informal buffer, josser
North American informal old coot
archaic grandsire, ancient
literary senex
1.1 (one's old man) informal A person’s father or a woman’s husband or boyfriend: when her old man left she moved in with Drummond...
- Its great to drink with your old man on fathers day
- So, your old man's a fraud
- Give your old man a kiss
Synonyms
husband, man
informal hubby, better half
British informal other half
humorous lord and master
archaic lord
1.2 (the old man) informal A man in authority over others, especially an employer or commanding officer: the old man wants a progress report...
- Dressed, we walked down to the office where the old man was already pouring a drink.
- Willie takes over the business but admits the old man as silent partner, as the two younger daughters become free to marry.
- And not to forget that as long as the old man is still the President of Swapo, all of us are actually financing the activities of Swapo.
Synonyms
captain, owner, boss, employer, foreman, manager, overseer, superintendent, director, controller, head, headman, principal
informal head honcho
British informal gaffer, guv'nor
North American informal sachem
1.3British informal An affectionate form of address between men or boys: are you all right, old man?...
- When asked by a policeman why he did it he replied, ‘sheer high spirits, old man.’
- Between you and me, old man, I'm glad they got me before it went any further.
- Well, they are your patrons, old man, so they do have some right to demand work from you.
1.4 informal Used with a surname instead of Mr: old man Roberts...
- The courtesans gathered, musicians played, and a feast like none had before witnessed was prepared to welcome back the Prince and to celebrate old man Clemantini.
2 another term for southernwood.There's a good cover of eucalyptus gum trees, lots of old man salt bush and we have a thirty mile frontage onto the Barwon River.