What is the exact concept of "Repulsion" and "Coupling" (Genetics)?
I guess the confusion is stemming from trying to fit the phenotypic terms coupling and repulsion to their genotypic basis.

Coupling and Repulsion are both used considering the phenotypic profile of the progeny, and hence, takes into consideration only the distribution of the dominant allele. If, in the progeny of the test cross, the percentage of double dominant is less than that the average percentage of single dominant, that would be what we call repulsion, as in the two dominant traits tend to be separated. The opposite, percentage of double dominant being greater than the average of individual dominant, is coupling. 

This said, it is clear what would be the corresponding genotypic states. If the chromosomal states are $Pr^+/Vg^+.. pr/vg$, coupling would be observed if the $pr$ and the $vg$ loci are linked, since for individual dominant phenotypes to appear, recombination is necessary which is rendered less probable due to linkage. A genotype of $Pr^+/vg..pr/Vg^+$ would result in the phenomenon of repulsion in a test cross. The case you cite, has the latter, and hence, we observe repulsion. 

Now to your questions.


  Is "Coupling" an exact synonym of "Linkage" ? and is "repulsion" an exact synonym of "recombinant"? No-where I could yet found mention of it.


Neither. More accurate would be to consider both coupling and repulsion as consequences of linkage, differing in the configuration of the linked gene (see above).


  What are they telling as coupling-"phase" and repulsion-"phase"? Are there 2 different "step"s or "time-frames" or "generations"? 


Although this is difficult to answer without knowing the context, I belive that the author here might be referring to the variable possible configuration of the alleles, as in, if they are in a coupling-phase, they are so oriented that the resultant progeny will show the coupling phenomenon. The phase may change to repulsion if a recombination event occurs. (again, see above.)


  Coupling and repulsion- are they indicating to a "phenomenon"? or the Genotypic "state"?  


Not to argue much in this semantic mashup, they are best viewed as differing phenomenon (as in the different obtained progeny phenotypic ratios) resulting from varied genotypic states.