a step-father figure. A man who has taken up the position of father for the child(ren) of a single mother, of whom said man is steadily dating.
A man who takes the responsibility of providing for a single mother and her young.
Hey, what's up with Mikey lately?" "oh, you know, he's become daddy on the spot. He's all busy making PB&J's and coaching soccer now.
A male figure who has taken the position of dad/father to a child(ren) who are born to a woman the male figure is romantically involved with.
A man who takes up the position of fathering young who are not his own biological children.
My mom got together with my step-dad when I was 7 and that dudes been daddy on the spot since then. He's like a real father to me.