Defination of Sajda as per shariah first understand what Sajda means in shariah , kissing of hands or feet of mother is not sajda, although kissing of hands of scholars is sunnah and feet is mubah[allowed only
Defination of prostration(sajda,bowing)
Sahih Muslim Book 4 Hadith 991
Ibn ‘Abbas reported: The Apostle of Allah (may peace be upon him) had been commanded that he should prostrate on the seven (bones) and he was forbidden to fold back the hair and clothing. And in the narration transmitted by Abu Rabi’ (the words are):” on the seven bones and I was forbidden to fold back the hair and clothing”.According to Abu’l-Rabi’ (the seven bones are):
The hands, the knees, and the (extremities) of the feet and the forehead.
Sajda doesnt means if you bow down to pick some thing up like your shoes and their is a person infront of you it will come into shirk or sajda,
Nor does if any one bows down a little infront of any one that comes into sajda as per shariah. Sajda according to Shariah defination is on seven bones , when all seven touch the ground ,, i hope thats clear here what does real prostration means acc to shariah